Capital Stock and Dividends - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended					12 Months Ended			1 Months Ended
	Nov. 23, 2010	Aug. 05, 2011	Nov. 23, 2010	Nov. 08, 2010	Oct. 07, 2010	Jun. 30, 2010 Year	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Feb. 29, 2012 Dividend Declared
Stockholders Equity Note [Line Items]
Common stock, shares authorized							200,000,000	200,000,000
Common stock, par value							$ 0.01	$ 0.01
Preferred stock, shares authorized							10,000,000
Preferred stock, par value							$ 0.01
Common stock Authorized for repurchase		$ 300,000,000				$ 300,000,000
Period of common stock repurchase						3
Repurchases of common stock							441,416
Dollar amount of common stock intended to purchase through modified dutch auction tender offer					175,000,000
Common stock repurchased, purchase price per share							$ 35.79
Common stock purchased through modified dutch auction tender offer - in shares				5,035,971
Common stock repurchased, total purchase price							15,797,000	247,825,000
Common stock purchased through modified dutch auction tender offer - price per share				$ 34.75
Common stock purchased through modified dutch auction tender offer - total purchase price in dollars				175,000,000
Fees and expenses incurred related to the modified dutch auction tender offer				800,000
Common stock purchased from stockholders under stock purchase agreement - in shares			2,071,509
Common stock purchased from stockholders under stock purchase agreement - price per share			$ 34.75
Common stock purchased from stockholders under stock purchase agreement - total purchase price in dollars			72,000,000
Common stock purchased from stockholders under stock purchase agreement and through tender offer - in shares	7,107,480
Percentage shares of common stock repurchased to outstanding common stock	9.20%
Common stock purchased from stockholders under stock purchase agreement and through tender offer- price per share	$ 34.75
Common stock purchased from stockholders under stock purchase agreement and through tender offer - total purchase price in dollars	247,000,000
Treasury shares issued							374,071	163,428	139,400
Average cost for restricted stock units							$ 6.63	$ 6.63	$ 6.63
Shares repurchased to satisfy employee withholding tax requirements resulting from certain restricted stock units becoming vested							142,080	51,038	44,802
Common stock repurchased, average cost							$ 36.58	$ 28.82	$ 24.79
Dividends declared on common stock							31,109,000	31,957,000	29,352,000
Treasury stock, shares							17,635,907	17,426,482
Cash dividend declared per share amount										$ 0.12
Cash dividend payable date										Mar. 26, 2012
Dividend payable, date of record for common stock holders										Mar. 12, 2012
Expected payment of quarterly dividend										$ 8,500,000