Computation of Basic and Diluted Net Profit Per Share Attributable to Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Disclosure Computation Of Basic And Diluted Net Profit Per Share Attributable To Common Stock [Abstract]
Net income	$ 51,367	$ 27,616	$ 142,061	$ 95,143
Weighted-average common shares outstanding, basic	79,977	79,808	79,920	80,173
Dilutive effect of potential common stock	1,489	1,284	1,603	1,403
Total shares, diluted	81,466	81,092	81,523	81,576
Net income per share, basic	$ 0.64	$ 0.35	$ 1.78	$ 1.19
Net income per share, diluted	$ 0.63	$ 0.34	$ 1.74	$ 1.17