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	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Earnings Attributable to Shareholders
Basic earnings attributable to shareholders	$ 88,490	$ 106,604	$ 249,152	$ 292,836
Diluted earnings attributable to shareholders	$ 88,490	$ 106,604	$ 249,152	$ 292,836
Weighted Average Shares
Weighted average basic shares outstanding	210,135,763	212,256,119	211,314,850	212,160,994
Effect of dilutive potential common shares	1,261,839	2,461,332	1,601,459	3,215,681
Weighted average diluted shares outstanding	211,397,602	214,717,451	212,916,309	215,376,675
Earnings Per Share
Basic earnings attributable to shareholders per share	$ 0.42	$ 0.50	$ 1.18	$ 1.38
Diluted earnings attributable to shareholders per share	$ 0.42	$ 0.50	$ 1.17	$ 1.36

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

9 Months Ended

Sep. 30, 2012

Sep. 30, 2011

Sep. 30, 2012

Sep. 30, 2011

Net Earnings Attributable to Shareholders

Basic earnings attributable to shareholders

$ 88,490

$ 106,604

$ 249,152

$ 292,836

Diluted earnings attributable to shareholders

$ 88,490

$ 106,604

$ 249,152

$ 292,836

Weighted Average Shares

Weighted average basic shares outstanding

210,135,763

212,256,119

211,314,850

212,160,994

Effect of dilutive potential common shares

1,261,839

2,461,332

1,601,459

3,215,681

Weighted average diluted shares outstanding

211,397,602

214,717,451

212,916,309

215,376,675

Earnings Per Share

Basic earnings attributable to shareholders per share

$ 0.42

$ 0.50

$ 1.18

$ 1.38

Diluted earnings attributable to shareholders per share

$ 0.42

$ 0.50

$ 1.17

$ 1.36

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