Earnings Per Share - Computation Of Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Basic earnings per share:
Net income	$ 59,295	$ 31,822	$ 183,428	$ 63,982
Weighted-average common shares outstanding	60,171	59,108	59,996	57,769
Basic earnings per share (in dollars per share)	$ 0.99	$ 0.54	$ 3.06	$ 1.11
Diluted earnings per share:
Net income	59,295	31,822	183,428	63,982
Senior Convertible Notes interest expense, net of tax	0	0	0	49
Numerator for diluted earnings per share	$ 59,295	$ 31,822	$ 183,428	$ 64,031
Shares used in computation:
Weighted-average common shares outstanding	60,171	59,108	59,996	57,769
Senior Convertible Notes shares	0	0	0	956
Employee stock options	1,649	1,882	1,673	1,853
Weighted-average number of shares - Diluted	61,820	60,990	61,669	60,578
Diluted earnings per share (in dollars per share)	$ 0.96	$ 0.52	$ 2.97	$ 1.06