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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Earnings Attributable to Shareholders
Basic earnings attributable to shareholders									$ 618,199	$ 489,345	$ 430,807
Diluted earnings attributable to shareholders									$ 618,199	$ 489,345	$ 430,807
Weighted Average Shares
Weighted average basic shares outstanding									174,133	179,247	181,282
Effect of dilutive potential common shares									3,700	2,419	1,422
Weighted average diluted shares outstanding									177,833	181,666	182,704
Earnings Per Share
Basic earnings attributable to shareholders per share	$ 1.04	$ 0.94	$ 0.80	$ 0.77	$ 0.94	$ 0.67	$ 0.60	$ 0.52	$ 3.55	$ 2.73	$ 2.38
Diluted earnings attributable to shareholders per share	$ 1.02	$ 0.92	$ 0.79	$ 0.76	$ 0.92	$ 0.66	$ 0.60	$ 0.51	$ 3.48	$ 2.69	$ 2.36