Repurchase of Common Stock (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Equity, Class of Treasury Stock [Line Items]
Shares repurchased	5,116	8,869	1,734
Aggregate repurchase price	$ 111,962	$ 215,071	$ 58,225
Average price paid per share	$ 21.89	$ 24.25	$ 33.58