Quarterly report pursuant to Section 13 or 15(d)

Stock Compensation - Summary of Nonvested Shares Related to Equity Incentive Plans (Detail)

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Stock Compensation - Summary of Nonvested Shares Related to Equity Incentive Plans (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Nonvested, Shares, Beginning of Period 1,263,833us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Granted, Shares 7,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Vested, Shares (130,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Cancelled, Shares 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Nonvested, Shares, End of Period 1,141,333us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Nonvested, Weighted Average Grant-Date Fair Value, Beginning of Period $ 43.38us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Granted, Weighted Average Grant-Date Fair Value $ 68.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Vested, Weighted Average Grant-Date Fair Value $ 27.54us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Cancelled, Weighted Average Grant-Date Fair Value $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Nonvested, Weighted Average Grant-Date Fair Value, End of Period $ 45.35us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue