Selected Quarterly Financial Data - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 48,258	$ 41,147	$ 56,702	$ 49,785	$ 56,053	$ 51,337	$ 59,296	$ 46,626	$ 195,892	$ 213,312	$ 236,707
Gross Profit	36,667	26,225	35,418	36,685	37,495	38,346	40,737	34,818	134,995	151,396
Income (Loss) from operations	2,897	(2,484)	9,233	12,169	15,726	18,402	183	2,305	21,815	36,616	$ 73,990
Net income (loss) attributable to common stockholders	$ 1,005	$ (2,390)	$ 6,725	$ 8,973	$ 12,588	$ 14,040	$ 2,659	$ 2,616	$ 14,313	$ 31,903
Earnings (loss) per share - basic (in dollars per share)	$ 0.08	$ (0.17)	$ 0.49	$ 0.64	$ 0.86	$ 0.94	$ 0.18	$ 0.18	$ 1.04	$ 2.16	$ 3.44
Earnings (loss) per share - diluted (in dollars per share)	$ 0.08	$ (0.17)	$ 0.48	$ 0.62	$ 0.84	$ 0.91	$ 0.17	$ 0.17	$ 1.01	$ 2.09	$ 3.27