Long-Term Debt - Convertible Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants	$ 0	$ 0	$ 14,100,000	$ 12,376,000
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	15,042,000	14,526,000	$ 11,955,000
Convertible due 2022 - Bond Hedge, Fair Value	0	2,062,000
Long-term debt	219,522,000	225,733,000
Convertible 2022 debt conversion liability	0	2,611,000
Convertible 2021 debt conversion liability	0	1,458,000
Convertible 2021 note hedge asset	$ 0	1,028,000
Convertible Senior Notes at 5.00% February 2024 | Convertible Subordinated Debt
Debt Disclosure [Abstract]
Initial conversion price	$ 14.78
Debt Instrument [Line Items]
Interest rate (as a percent)	5.00%
Debt Instrument, Face Amount	$ 72,909,000
Effective Interest Rate	8.77%
Unamortized discount	$ (10,733,000)
Long-term debt	60,817,000	0
Debt Instrument, Non-Cash Interest Expense Recognized in the Period	205,000
Debt Instrument, Increase, Accrued Interest	456,000
Debt Instrument, Fee Amount, Net Balance Shown as a Liability	(1,359,000)
Debt Instrument, Net Carrying Amount	$ 60,817,000
Convertible Senior Notes at 5.00% February 2021 | Convertible Subordinated Debt
Debt Disclosure [Abstract]
Initial conversion price	$ 16.65
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants				$ 12,376,000
Interest rate (as a percent)	5.00%			5.00%
Debt Instrument, Face Amount	$ 61,091,000	150,000,000		$ 150,000,000
Convertible Debt Conversion Feature, Fair Value at Issuance	$ 34,480,000
Effective Interest Rate	11.10%
Unamortized discount	$ (3,916,000)	(17,193,000)
Long-term debt	56,628,000	130,260,000
Convertible Debt Conversion Feature Gain (Loss)	(2,210,000)	51,696,000
Convertible due 2021 - Bond Hedge, Fair Value at Issuance	27,975,000
Convertible Debt Note Hedge Gain (Loss)	2,852,000	(45,887,000)
Debt Instrument, Non-Cash Interest Expense Recognized in the Period	6,672,000	6,706,000
Debt Instrument, Increase, Accrued Interest	6,803,000	7,500,000
Debt Instrument, Fee Amount, Net Balance Shown as a Liability	(547,000)	(2,547,000)
Debt Instrument, Net Carrying Amount	$ 56,628,000	$ 130,260,000