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Stock Based Compensation (Details 2) (USD $)
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3 Months Ended |
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Mar. 31, 2015
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Nonvested at January 1, 2015 | 733,628us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber |
| RSU Granted | 330,173us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod |
| RSUs forfeited | (58,522)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod |
| Shares of common stock issued in exchange for RSUs | (42,470)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod |
| Nonvested at March 31, 2015 | 962,809us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber |
| Weighted Average Grant Date Fair Value, Nonvested at January 1, 2015 | $ 10.49us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, RSU Granted | $ 9.89us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, RSUs forfeited | $ 8.66us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, Shares of common stock issued in exchange for RSUs | $ 12.08watt_SharebasedPaymentAwardEquityInstrumentsOtherThanOptionsSharesIssuedInPeriodWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, Nonvested at March 31, 2015 | $ 10.33us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, Vested at January 1, 2015 | $ 9.94watt_SharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, RSUs vested | $ 11.15us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, Shares of common stock issued in exchange for RSUs | $ 12.08watt_SharebasedPaymentAwardEquityInstrumentsOtherThanOptionsSharesIssuedInPeriodWeightedAverageGrantDateFairValue |
| Weighted Average Grant Date Fair Value, Vested at March 31, 2015 | $ 10.65watt_SharebasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue |
| Vested at January 1, 2015 | 6,349us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber |
| RSUs vested | 130,772us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod |
| Shares of common stock issued in exchange for RSUs | (42,470)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod |
| Vested at March 31, 2015 | 94,651us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber |
| X | ||||||||||
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- Definition
The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Definition
As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Number of share instruments newly issued under a share-based compensation plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The weighted average fair value at grant date for vested equity-based awards issued during the period on other than stock (or unit) option plans. No definition available.
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| X | ||||||||||
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- Definition
The weighted average fair value of vested awards on equity-based plans excluding option plans. No definition available.
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