Selected Quarterly Financial Data - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Net	$ 370,124	$ 343,236	$ 331,514	$ 247,739	$ 95,688	$ 97,108	$ 96,721	$ 89,855
Gross Profit	137,490	111,598	88,062	88,945	50,760	51,273	50,132	49,233	$ 426,095	$ 201,398	$ 180,797
Net Income	$ 49,705	$ 136	$ (37,060)	$ 55,863	$ 9,512	$ 18,806	$ 16,606	$ 18,160	$ 68,644	$ 63,084	$ 44,985
Basic	$ 2.47	$ 0.01	$ (1.87)	$ 3.03	$ 0.58	$ 1.16	$ 1.03	$ 1.13	$ 3.50	$ 3.90	$ 2.84
Diluted	$ 2.33	$ 0.01	$ (1.87)	$ 2.86	$ 0.54	$ 1.09	$ 0.98	$ 1.08	$ 3.29	$ 3.66	$ 2.73