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.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- 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).

Stock-Based Compensation - Equity Awards Outstanding and Exercisable (Detail) - $ / shares	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Stock Option
Options Outstanding
Options, Outstanding at beginning of period (in shares)	1,344,795
Options, Granted (in shares)	0
Options, Exercised (in shares)	(52,683)
Options, Forfeited (in shares)	(36,300)
Options, Outstanding at end of period (in shares)	1,255,812		1,344,795
Options, Exercisable (in shares)	1,005,812
Options, Weighted Average Exercise Price
Options, Weighted Average Exercise Price, at beginning of period (in usd per share)	$ 11.70
Options, Weighted Average Exercise Price, Granted (in usd per share)	0.00
Options, Weighted Average Exercise Price, Exercised (in usd per share)	9.22
Options, Weighted Average Exercise Price, Forfeited (in usd per share)	20.11
Options, Weighted Average Exercise Price, at end of period (in usd per share)	11.57		$ 11.70
Options, weighted average exercise price, exercisable (in usd per share)	11.09
Options, Weighted Average Grant Date Fair Value
Options, Weighted Average Grant Date Fair Value at beginning of period (in usd per share)	6.04
Options, Weighted Average Grant Date fair Value, Granted (in usd per share)	0.00
Options, Weighted Average Grant Date fair Value, Exercised (in usd per share)	3.55
Options, Weighted Average Grant Date fair Value, Forfeited(in usd per share)	9.56
Options, Weighted Average Grant Date Fair Value at end of period (in usd per share)	5.57		$ 6.04
Options, Weighted Average Grant Date fair Value, Exercisable (in usd per share)	$ 5.29
Options, Weighted Average Remaining Term
Options, Outstanding, Weighted Average Remaining Term	6 years 2 months 12 days		6 years 10 months 2 days
Options, Exercisable, Weighted Average Remaining Term	6 years 1 month 2 days
Stock Option \| Minimum
Options, Weighted Average Exercise Price
Options, Weighted Average Exercise Price, at beginning of period (in usd per share)	$ 2.68
Options, Weighted Average Exercise Price, Granted (in usd per share)	0.00
Options, Weighted Average Exercise Price, Exercised (in usd per share)	2.68
Options, Weighted Average Exercise Price, Forfeited (in usd per share)	12.10
Options, Weighted Average Exercise Price, at end of period (in usd per share)	2.68		$ 2.68
Options, weighted average exercise price, exercisable (in usd per share)	2.68
Stock Option \| Maximum
Options, Weighted Average Exercise Price
Options, Weighted Average Exercise Price, at beginning of period (in usd per share)	27.87
Options, Weighted Average Exercise Price, Granted (in usd per share)	0.00
Options, Weighted Average Exercise Price, Exercised (in usd per share)	27.87
Options, Weighted Average Exercise Price, Forfeited (in usd per share)	27.87
Options, Weighted Average Exercise Price, at end of period (in usd per share)	27.87		$ 27.87
Options, weighted average exercise price, exercisable (in usd per share)	$ 27.87
Restricted Stock Units
Restricted Stock Units, shares
Restricted Stock Units, shares at beginning of period (in shares)	692,823
Restricted Stock Units, shares, Granted (in shares)	35,413
Restricted Stock Units, shares, Vested (in shares)	(219,587)
Restricted Stock Units, shares, Forfeited (in shares)	(32,093)
Restricted Stock Units, shares at end of period (in shares)	476,556		692,823
Restricted Stock, Weighted Average Grant Date Fair Value
Restricted Stock, Weighted Average Grant Date Fair Value at beginning of period (in usd per share)	$ 15.23
Restricted Stock, Weighted Average Grant Date Fair Value, Granted (in usd per share)	39.42
Restricted Stock, Weighted Average Grant Date Fair Value, Vested (in usd per share)	14.88
Restricted Stock, Weighted Average Grant Date Fair Value, Forfeited (in usd per share)	29.03
Restricted Stock, Weighted Average Grant Date Fair Value at end of period (in usd per share)	$ 16.31		$ 15.23
Performance-based Restricted Stock Units
Restricted Stock Units, shares
Restricted Stock Units, shares at beginning of period (in shares)	1,563,951
Restricted Stock Units, shares, Granted (in shares)	291,770
Restricted Stock Units, shares, Vested (in shares)	(79)	0
Restricted Stock Units, shares, Forfeited (in shares)	(3,418)
Restricted Stock Units, shares at end of period (in shares)	1,852,224		1,563,951
Restricted Stock, Weighted Average Grant Date Fair Value
Restricted Stock, Weighted Average Grant Date Fair Value at beginning of period (in usd per share)	$ 20.86
Restricted Stock, Weighted Average Grant Date Fair Value, Granted (in usd per share)	29.32
Restricted Stock, Weighted Average Grant Date Fair Value, Vested (in usd per share)	27.61
Restricted Stock, Weighted Average Grant Date Fair Value, Forfeited (in usd per share)	28.47
Restricted Stock, Weighted Average Grant Date Fair Value at end of period (in usd per share)	$ 22.19		$ 20.86