Stock Options and Other Equity-Based Incentive Instruments - Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of Shares, beginning balance	1,246,370
Options granted, Number of Shares
Options exercised, Number of Shares	(166,020)
Options forfeited, Number of Shares
Options outstanding, Number of Shares, ending balance	1,080,350
Options outstanding, Weighted Average Exercise Price, beginning balance	$ 18.04
Options granted, Weighted Average Exercise Price
Options exercised, Weighted Average Exercise Price	$ 17.32
Options forfeited, Weighted Average Exercise Price
Options outstanding, Weighted Average Exercise Price, ending balance	$ 18.15
Outstanding, Weighted Average Fair Value on Date of Grant, beginning balance
Options granted, Weighted Average Fair Value on Date of Grant
Options exercised, Weighted Average Fair Value on Date of Grant
Options forfeited, Weighted Average Fair Value on Date of Grant
Outstanding, Weighted Average Fair Value on Date of Grant, ending balance
Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Option Price per Share, beginning balance	$ 12.63
Options granted, Option Price per Share
Options exercised, Option Price per Share	$ 14.54
Options forfeited, Option Price per Share
Options outstanding, Option Price per Share, ending balance	$ 12.63
Maximum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Option Price per Share, beginning balance	$ 25.91
Options granted, Option Price per Share
Options exercised, Option Price per Share	$ 20.58
Options forfeited, Option Price per Share
Options outstanding, Option Price per Share, ending balance	$ 25.91