Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Stock Option Activity (Detail)

v2.4.1.9
Stock Based Compensation - Stock Option Activity (Detail) (USD $)
In Millions, except Share data in Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward      
Number of Shares Underlying Options, Outstanding at beginning of period 4,927us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber    
Number of Shares Underlying Options, Granted 1,118us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 1,836us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 1,024us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Number of Shares Underlying Options, Exercised (1,128)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised (877)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised (759)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Number of Shares Underlying Options, Forfeited (152)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod    
Number of Shares Underlying Options, Outstanding at end of period 4,765us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 4,927us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Number of Shares Underlying Options, Vested - end of period 3,318egy_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber    
Number of Shares Underlying Options, Vested and expected to vest - end of period 4,728us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber    
Weighted Average Exercise Price Per Share, Outstanding at beginning of period $ 6.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Granted $ 7.05us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Exercised $ 5.04us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 4.25us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 4.62us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Weighted Average Exercise Price Per Share, Forfeited $ 7.47us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Outstanding at end of period $ 7.41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 6.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Weighted Average Exercise Price Per Share, Vested - end of period $ 7.45egy_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Vested and expected to vest - end of period $ 7.41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice    
Weighted Average Remaining Contractual Term, Outstanding balance 2 years 7 months 13 days 2 years 10 months 6 days  
Weighted Average Remaining Contractual Term, Granted 4 years 2 months 5 days    
Weighted Average Remaining Contractual Term, Exercised 8 months 9 days    
Weighted Average Remaining Contractual Term, Forfeited 3 years 6 months 15 days    
Weighted Average Remaining Contractual Term, Exercisable at end of period 2 years 7 months 13 days 2 years 10 months 6 days  
Weighted Average Remaining Contractual Term, Vested - end of period 2 years 2 months 19 days    
Weighted Average Remaining Contractual Term, Vested and expected to vest - end of period 2 years 7 months 13 days    
Aggregate Intrinsic Value, Outstanding at beginning of period $ 2.81us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue    
Aggregate Intrinsic Value, Outstanding at end of period 1.61us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue 2.81us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue  
Aggregate Intrinsic Value, Vested - end of period 1.18egy_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingAggregateIntrinsicValue    
Aggregate Intrinsic Value, Vested and expected to vest - end of the period $ 1.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue