Net Profit per Share - Computation of Basic and Diluted Net Profit Per Share Attributable to Common Stock (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 442,776	$ 400,235	$ 231,418
Denominator:
Weighted-average common shares outstanding, basic (shares)	79,424	80,064	80,085
Dilutive effect of potential common stock (shares)	676	1,293	1,747
Total shares, diluted (shares)	80,100	81,357	81,832
Net income per share, basic (usd per share)	$ 5.57	$ 5.00	$ 2.89
Net income per share, diluted (usd per share)	$ 5.53	$ 4.92	$ 2.83