Equity (Detail) - Share Repurchase Activity (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Number of shares repurchased (1)	95,833	[1]	1,543,069	[1]	2,260,093	[1]	3,886,521	[1]
Cost of repurchased shares (in thousands) (in Dollars)	$ 4,626		$ 53,354		$ 89,300		$ 141,214

[1] The average purchase price for the shares was $48.27 and $39.51 for the three and nine months ended September 30, 2012 respectively, and $34.58 and $36.33 for the three and nine months ended September 30, 2011, respectively.