Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income	$ 21,361	$ 11,777	$ 36,760	$ 16,903
Weighted-average common shares outstanding - basic	49,131	49,028	49,105	48,890
Effect of diluted stock options and unvested restricted stock	430	800	318	798
Weighted-average common shares outstanding - diluted	49,561	49,828	49,423	49,688
Net income per share: Basic	$ 0.43	$ 0.24	$ 0.75	$ 0.35
Net income per share: Diluted	$ 0.43	$ 0.24	$ 0.74	$ 0.34
Anti-dilutive shares not included above	1,704	628	1,704	574
Convertible Notes [Member]
Debt Instrument, Convertible, Conversion Price	$ 30.25		$ 30.25