Long-Term Debt - Convertible Senior Notes Due 2022 (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 May 2022
Debt Instrument [Line Items]
Interest rate (as a percent)		4.25%
Frequency of periodic payment		semi-annually
Maturity date		May 01, 2022
Initial conversion ratio		0.0719748
Initial conversion price per share (in dollars per share) | $ / shares		$ 13.89
Redemption price as a percentage of principal amount		100.00%
Minimum percentage in aggregate principal amount		25.00%
Repurchased principal amount	$ 90,000
Repurchase amount	89,100
Reacquisition of debt component	81,700
Gain (loss) on extinguishment of long-term debt	3,300
Unamortized debt discount		$ (1,325)	(8,000)
Reacquisition of equity component	$ 7,400
Carrying amount of equity component		9,500	16,900
Carrying amount of equity component, net of tax		$ 5,300	11,000
Effective interest rate (as a percent)		7.30%
Interest expense		$ 6,200	$ 8,400	$ 8,100