Net Profit per Share - Computation of Basic and Diluted Net Profit Per Share Attributable to Common Stock (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income	$ 145,832	$ 64,295	$ 58,691
Denominator:
Weighted-average common shares outstanding, basic (shares)	80,754	80,551	80,529
Dilutive effect of potential common stock (shares)	1,529	2,038	2,511
Total shares, diluted (shares)	82,283	82,589	83,040
Net income per share, basic (usd per share)	$ 1.81	$ 0.80	$ 0.73
Net income per share, diluted (usd per share)	$ 1.77	$ 0.78	$ 0.71