Debt - Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Non-Cash Interest Expense
Amortization of debt discount/transaction costs	$ 13,819	$ 13,792	$ 12,676
Total Interest Expense	26,282	24,640	21,991
2023 Notes
Cash Interest Expense
Coupon interest expense	3,138	7,390	9,315
Non-Cash Interest Expense
Amortization of debt discount/transaction costs	4,932	10,887	$ 12,676
Estimated fair value	$ 20,400
Convertible Debt, Fair Value by Fair Value Hierarchy Level	Level 2
2025 Notes
Cash Interest Expense
Coupon interest expense	$ 4,637	554
Non-Cash Interest Expense
Amortization of debt discount/transaction costs	4,795	546
Estimated fair value	$ 175,000
Convertible Debt, Fair Value by Fair Value Hierarchy Level	Level 2
2027 Notes
Cash Interest Expense
Coupon interest expense	$ 4,688	2,904
Non-Cash Interest Expense
Amortization of debt discount/transaction costs	4,092	$ 2,359
Estimated fair value	$ 258,900
Convertible Debt, Fair Value by Fair Value Hierarchy Level	Level 2