Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	Nov. 30, 2012	Oct. 24, 2011	Dec. 03, 2010	Feb. 28, 2010	Dec. 31, 2012	Dec. 31, 2011
Stockholders Equity Note [Line Items]
Special cash dividend declared, date	Nov. 05, 2012	Oct. 24, 2011	Dec. 03, 2010	Feb. 01, 2010
Special cash dividend record, date	Nov. 23, 2012	Dec. 19, 2011	Dec. 17, 2010	Feb. 16, 2010
Special cash dividend declared per share	$ 0.25	$ 0.25	$ 0.25	$ 0.30
Special cash dividend paid	$ 16.3	$ 16.2	$ 16.2	$ 19.3
Special cash dividend paid, date	Dec. 05, 2012	Jan. 03, 2012	Dec. 30, 2010	Feb. 26, 2010
Outstanding shares of common stock	64,623,372	64,173,368	63,701,118	63,276,943	64,628,105	64,178,101
Dividend equivalent paid per share on unvested shares of restricted stock outstanding on the dividend record date granted under the Company's 2006 Stock Option and Incentive Plan	$ 0.25	$ 0.25	$ 0.25	$ 0.30
Unvested shares of restricted stock on the dividend record date	727,354	750,497	1,056,117	1,099,352