Equity (Detail) - Share Repurchase Activity (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Stockholders' Equity Note [Abstract]
Number of shares repurchased	1,124,117	[1]	1,016,978	[1]	5,350,915	[1]	2,859,246	[1]
Cost of repurchased shares	$ 79,678	[2]	$ 59,252	[2]	$ 387,126	[2]	$ 157,251	[2]

[1] The average purchase price for the shares was $72.94 and $70.67 for the three and nine months ended September 30, 2014, respectively, and $58.26 and $55.00 for the three and nine months ended September 30, 2013, respectively.

[2] The cost of repurchased shares for the nine months ended September 30, 2014 includes payment for share repurchase transactions that occurred in late December 2013 but were paid in early January 2014.