Earnings per Share (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
Net income	$ 28,801	$ 19,677	$ 65,561	$ 36,580
Weighted-average common shares outstanding - basic	49,185	49,070	49,132	48,951
Effect of diluted stock options and unvested restricted stock	915	705	517	767
Weighted-average common shares outstanding - diluted	50,100	49,775	49,649	49,718
Net income per share: Basic	$ 0.59	$ 0.40	$ 1.33	$ 0.75
Net income per share: Diluted	$ 0.57	$ 0.40	$ 1.32	$ 0.74
Anti-dilutive shares not included above	610	1,580	1,339	909
Convertible Notes [Member]
Debt Instrument, Convertible, Conversion Price	$ 30.25		$ 30.25