Equity (Detail) - Share Repurchase Activity (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Stockholders' Equity Note [Abstract]
Number of shares repurchased	1,016,978	[1]	95,833	[1]	2,859,246	[1]	2,260,093	[1]
Cost of repurchased shares	$ 59,252		$ 4,626		$ 157,251		$ 89,300

[1] The average purchase price for the shares was $58.26 and $55.00 for the three and nine months ended September 30, 2013, respectively, and $48.27 and $39.51 for the three and nine months ended September 30, 2012, respectively.