Basic and Diluted Earnings per Share - Numerator and Denominator of the Basic and Diluted Per Share Computations for Earnings Attributable to Shareholders Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net Earnings Attributable to Shareholders
Basic earnings attributable to shareholders	$ 83,955	$ 95,000	$ 160,662	$ 186,232
Diluted earnings attributable to shareholders	$ 83,955	$ 95,000	$ 160,662	$ 186,232
Weighted Average Shares
Weighted average basic shares outstanding	211,724,082	212,136,164	211,910,872	212,112,643
Effect of dilutive potential common shares	1,488,830	3,522,879	1,772,715	3,667,587
Weighted average diluted shares outstanding	213,212,912	215,659,043	213,683,587	215,780,230
Earnings Per Share
Basic earnings attributable to shareholders	$ 0.40	$ 0.45	$ 0.76	$ 0.88
Diluted earnings attributable to shareholders	$ 0.39	$ 0.44	$ 0.75	$ 0.86