Debt - Outstanding Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Oct. 01, 2021	Sep. 30, 2021	Dec. 31, 2020	May 31, 2018	Jul. 31, 2017	Jul. 05, 2017
Gross Amount
Total	$ 316,250		$ 316,250	$ 317,066
Less current portion	0		0	213
Total long-term debt	316,250		316,250	316,853
Debt Discount and Issuance Costs
Total	(4,406)		(52,064)	(62,531)
Less current portion	0		0	0
Total long-term debt	(4,406)		(52,064)	(62,531)
Carrying Amount
Total	311,844	$ 311,471	264,186	254,535
Less current portion	0		0	213
Total long-term debt	311,844		264,186	254,322
2024 Convertible Notes
Carrying Amount
Stated interest rate						2.875%	2.875%
Senior Notes | 2024 Convertible Notes
Gross Amount
Total	143,750		143,750	143,750
Debt Discount and Issuance Costs
Total	(1,644)		(20,207)	(25,014)
Carrying Amount
Total	142,106		123,543	118,736
Senior Notes | 2025 Convertible Notes
Gross Amount
Total	172,500		172,500	172,500
Debt Discount and Issuance Costs
Total	(2,762)		(31,857)	(37,517)
Carrying Amount
Total	169,738		140,643	134,983
Stated interest rate					2.375%
Unsecured Debt | 8.5% unsecured debt due 2024
Gross Amount
Total	0		0	816
Debt Discount and Issuance Costs
Total	0		0	0
Carrying Amount
Total	$ 0		$ 0	$ 816
Stated interest rate	8.50%