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	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Redeemable Preferred Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance	$ 8,063	$ 5,247
Change in fair value	7,375	(2,082)
Balance	15,438	3,165
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	(5,631)	0
Change in fair value	9,047	(7,675)
Payment-in-kind interest	158	667
Balance	$ 37,708	$ 43,745