Earnings Per Share - Summary of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 202,823	$ 129,618	$ 457,503	$ 356,961
Denominator for basic earnings per share (in shares)	90,751	92,631	91,619	92,604
Dilutive securities (in shares)	2,250	2,676	2,304	2,600
Denominator for diluted earnings per share (in shares)	93,001	95,307	93,923	95,204
Basic earnings per share (in dollars per share)	$ 2.23	$ 1.40	$ 4.99	$ 3.85
Diluted earnings per share (in dollars per share)	$ 2.18	$ 1.36	$ 4.87	$ 3.75