Computation of Basic and Diluted Net Profit Per Share Attributable to Common Stock (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Net profit (loss)	$ 34,537	$ (344)	$ 21,874	$ 49,132
Denominator:
Weighted-average common shares outstanding, basic (in shares)	79,967	81,437	80,592	80,356
Dilutive effect of potential common stock (in shares)	1,881	0	1,957	2,660
Total shares, diluted	81,848	81,437	82,549	83,016
Net profit (loss) per share, basic	$ 0.43	$ 0.00	$ 0.27	$ 0.61
Net profit (loss) per share, diluted	$ 0.42	$ 0.00	$ 0.26	$ 0.59