Long-Term Debt Components of Convertible Debt (Details) - USD ($)	3 Months Ended					9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2017	Mar. 31, 2016	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Issuance of warrants					$ 12,376,000
Long-term debt	$ 242,264,000	$ 219,522,000				$ 242,264,000
Convertible Subordinated Debt | Convertible Senior Notes at 5.00% February 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Increase, Accrued Interest	241,000		$ 1,834,000			1,617,000	$ 5,584,000
Debt Instrument, Face Amount	$ 1,250,000	61,091,000			$ 150,000,000	$ 1,250,000
Interest rate (as a percent)	5.00%					5.00%
Unamortized discount	$ (22,000)	(3,916,000)				$ (22,000)
Long-term debt	1,224,000	56,628,000				1,224,000
Debt fees	(4,000)	(547,000)				(4,000)
Debt Instrument, Net Carrying Amount	1,224,000	56,628,000				1,224,000
Convertible Subordinated Debt | Convertible Senior Notes at 4.50% February 2022 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Increase, Accrued Interest	917,000		$ 1,350,000			3,487,000	$ 4,050,000
Debt Instrument, Face Amount	$ 81,500,000	120,000,000		$ 120,000,000		$ 81,500,000
Issuance of warrants				$ 14,100,000
Interest rate (as a percent)	4.50%					4.50%
Unamortized discount	$ (7,837,000)	(16,027,000)				$ (7,837,000)
Long-term debt	72,652,000	101,815,000				72,652,000
Debt fees	(1,011,000)	(2,158,000)				(1,011,000)
Debt Instrument, Net Carrying Amount	72,652,000	101,815,000				72,652,000
Convertible Subordinated Debt | Convertible Senior Notes at 5.00% November 2024 [Domain]
Debt Instrument [Line Items]
Long-term debt	62,443,000	60,817,000				62,443,000
Convertible Subordinated Debt | Convertible Senior Notes at 5.00% November 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Increase, Accrued Interest	912,000					2,735,000
Debt Instrument, Loss on Exchange		5,885,000
Debt Instrument, Face Amount	$ 72,909,000	$ 72,909,000				$ 72,909,000
Interest rate (as a percent)	5.00%	5.00%				5.00%
Unamortized discount	$ (9,363,000)	$ (10,733,000)				$ (9,363,000)
Debt fees	(1,103,000)	(1,359,000)				(1,103,000)
Debt Instrument, Net Carrying Amount	$ 62,443,000	$ 60,817,000				$ 62,443,000