Fair Value Measurements - Reconciliation of Beginning and Ending Balances of Assets Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on extinguishment of convertible senior notes	$ 13,205	$ 453	$ 611
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additions	7,250	0
Loss on extinguishment of convertible senior notes	10,417	453
Extinguishment of convertible senior notes	(48,170)	0
Change in fair value	2,529	(2,948)
3.25% Convertible Senior Notes Due 2020 | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
New issuance (Series A preferred stock)	0	8,000
3.25% Convertible Senior Notes Due 2023 | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	0	0
New issuance (Series A preferred stock)	4,894	0
Change in fair value	353	0
Ending Balance	5,247	0	0
3.25% Convertible Senior Notes Due 2023 | Fair Value Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	0	0
New issuance (Series A preferred stock)	37,916	0
Change in fair value	2,583	0
Ending Balance	50,753	0	0
Oasis Management and Oasis Investments ll Master Fund Ltd. | 3.25% Convertible Senior Notes Due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
New issuance (Series A preferred stock)	10,254	0
Carrying Amount | 3.25% Convertible Senior Notes Due 2020 | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	27,974	22,469
Ending Balance	$ 0	$ 27,974	$ 22,469