Long-Term Debt - Convertible Senior Notes Due 2026 (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Aug. 14, 2020 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Principal amount		$ 404,732
Interest expense		30,538	$ 31,186	$ 32,617
Unamortized debt discount		$ (45,692)	(22,540)
2026 Capped Calls
Debt Instrument [Line Items]
Initial cap price (in dollars per share) | $ / shares		$ 8.42
Convertible Senior Notes Maturing February 2026
Debt Instrument [Line Items]
Principal amount	$ 200,000	$ 200,000	0
Proceeds from debt, net of issuance costs	192,500
Net proceeds used to fund the cost of capped call transactions	$ 10,500
Interest rate (as a percent)	6.75%
Frequency of periodic payment	semi-annually
Maturity date		Feb. 15, 2026
Initial conversion ratio		0.1433795
Initial conversion price per share (in dollars per share) | $ / shares	$ 6.97
Redemption price as a percentage of principal amount	100.00%
Minimum percentage in aggregate principal amount	25.00%
Carrying amount of equity component		$ 43,800
Carrying amount of equity component, net of tax		$ 34,600
Effective interest rate (as a percent)		12.40%
Interest expense		$ 7,200
Unamortized debt discount		(41,716)
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Principal amount		$ 35,000	125,000
Repurchased principal amount	$ 90,000
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%
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
Unamortized debt discount		(1,325)	(8,000)
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Principal amount		$ 30,000	125,000
Repurchased principal amount	$ 95,000
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%
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
Unamortized debt discount		$ (2,651)	$ (14,500)