Shares Repurchased (Detail) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Share Repurchases [Line Items]
Number of shares repurchased	10.7		10.6	[1]	20.6	[2]
Average price per share	$ 37.15		$ 26.60	[1]	$ 23.71	[2]
Total cost of repurchases	$ 397,376	[3]	$ 282,873	[1],[3]	$ 489,254	[2],[3]

[1] On a reverse split adjusted basis the number of shares repurchased was 5.3 million for $53.20 per share.

[2] On a reverse split adjusted basis the number of shares repurchased was 10.3 million for $47.42 per share.

[3] Amount excludes transaction costs.