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 ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Earnings Attributable to Shareholders
Basic earnings attributable to shareholders									$ 696,140	$ 590,395	$ 618,199
Diluted earnings attributable to shareholders									$ 696,140	$ 590,395	$ 618,199
Weighted Average Shares
Weighted average basic shares outstanding									168,333	170,899	174,133
Effect of dilutive potential common shares									2,563	3,310	3,700
Weighted average diluted shares outstanding									170,896	174,209	177,833
Earnings Per Share [Abstract]
Basic earnings attributable to shareholders per share	$ 1.17	$ 1.14	$ 1.10	$ 0.73	$ 0.81	$ 0.94	$ 0.90	$ 0.81	$ 4.14	$ 3.45	$ 3.55
Diluted earnings attributable to shareholders per share	$ 1.16	$ 1.12	$ 1.09	$ 0.71	$ 0.79	$ 0.92	$ 0.88	$ 0.80	$ 4.07	$ 3.39	$ 3.48