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Stock Based Compensation (Details 2) (USD $)
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12 Months Ended |
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Dec. 31, 2014
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Dec. 31, 2013
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Exercise Price |
$ 4.41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
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$ 1.68us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
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| Number of Options, Outstanding |
1,607,075us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
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275,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
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| Weighted Average Remaining Life In Years |
9 years 1 month 6 days
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| Number of Options, Exercisable |
550,298us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
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17,231us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
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| Stock Option One [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Exercise Price |
$ 1.68us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= watt_StockOptionOneMember
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| Number of Options, Outstanding |
275,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionOneMember
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| Weighted Average Remaining Life In Years |
8 years 10 months 24 days
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| Number of Options, Exercisable |
86,153us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionOneMember
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| Stock Option Two [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Exercise Price |
$ 2.49us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= watt_StockOptionTwoMember
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| Number of Options, Outstanding |
326,754us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionTwoMember
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| Weighted Average Remaining Life In Years |
9 years
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| Number of Options, Exercisable |
115,627us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionTwoMember
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| Stock Option Three [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Exercise Price |
$ 3.63us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= watt_StockOptionThreeMember
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| Number of Options, Outstanding |
51,958us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionThreeMember
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| Weighted Average Remaining Life In Years |
9 years 2 months 12 days
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| Number of Options, Exercisable |
51,958us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionThreeMember
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| Stock Option Four [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Exercise Price |
$ 4.99us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= watt_StockOptionFourMember
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| Number of Options, Outstanding |
99,214us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionFourMember
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| Weighted Average Remaining Life In Years |
9 years 2 months 12 days
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| Number of Options, Exercisable |
19,013us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionFourMember
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| Stock Option Five [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Exercise Price |
$ 6.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= watt_StockOptionFiveMember
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| Number of Options, Outstanding |
853,460us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionFiveMember
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| Weighted Average Remaining Life In Years |
9 years 2 months 12 days
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| Number of Options, Exercisable |
277,547us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= watt_StockOptionFiveMember
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