Fair Value Measurements (Details) - Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation - Fair Value, Recurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Redeemable Preferred Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance	$ 8,062	$ 5,247
Change in fair value	8,914	(2,083)
Balance	16,976	3,164
3.25% Convertible Senior Notes Due 2023 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance	34,134	50,753
Conversion of convertible senior notes	(19,872)	(9,473)
Change in fair value	12,844	52
Payment-in-kind interest	285	925
Balance	$ 27,391	$ 42,257