Shares Repurchased (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Share Repurchases [Line Items]
Number of shares repurchased	7,040,621		9,259,400		10,690,657
Average price per share	$ 76.26		$ 55.59		$ 37.15
Total cost of repurchases	$ 537,088	[1]	$ 514,907	[1]	$ 397,376	[1]

[1] Amount excludes transaction costs.