Stock Options and Other Equity-Based Incentive Instruments - Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options granted, Weighted Average Fair Value on Date of Grant	$ 8.91
Options outstanding, Weighted Average Exercise Price, beginning balance	$ 17.07
Options granted, Weighted Average Exercise Price	$ 19.31
Options exercised, Weighted Average Exercise Price	$ 13.03
Options forfeited, Weighted Average Exercise Price	$ 24.23
Options outstanding, Weighted Average Exercise Price, ending balance	$ 18.06
Options outstanding, Number of Shares, beginning balance	1,393,935
Options granted, Number of Shares	144,500
Options exercised, Number of Shares	(248,765)
Options forfeited, Number of Shares	(8,000)
Options outstanding, Number of Shares, ending balance	1,281,670
Minimum [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Option Price per Share, beginning balance	$ 12.60
Options granted, Option Price per Share	$ 16.59
Options exercised, Option Price per Share	$ 12.60
Options forfeited, Option Price per Share	$ 22.54
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	$ 19.46
Options exercised, Option Price per Share	$ 20.58
Options forfeited, Option Price per Share	$ 25.91
Options outstanding, Option Price per Share, ending balance	$ 25.91