Long-Term Debt - Convertible Senior Notes Due 2023 (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Aug. 14, 2020 USD ($)	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Gain (loss) on extinguishment of long-term debt		$ 9,239	$ (18)	$ (1,183)
Unamortized debt discount		(45,692)	(22,540)
Interest expense		$ 30,538	31,186	32,617
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Interest rate (as a percent)		4.125%
Frequency of periodic payment		semi-annually
Maturity date		Sep. 15, 2023
Initial conversion ratio		0.1056133
Initial conversion price per share (in dollars per share) | $ / shares		$ 9.47
Redemption price as a percentage of principal amount		100.00%
Minimum percentage in aggregate principal amount		25.00%
Repurchased principal amount	$ 95,000
Repurchase amount	94,100
Reacquisition of debt component	78,200
Gain (loss) on extinguishment of long-term debt	5,900
Unamortized debt discount		$ (2,651)	(14,500)
Reacquisition of equity component	$ 15,900
Carrying amount of equity component		4,200	20,100
Carrying amount of equity component, net of tax		$ 3,600	15,900
Effective interest rate (as a percent)		7.80%
Interest expense		$ 6,100	$ 8,400	$ 6,400