Long-Term Debt - Convertible Senior Notes Due 2026 (Details) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 14, 2020 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Principal amount		$ 414,535		$ 414,535
Repurchase amount	$ 183,200
Interest expense		8,007	$ 7,694	22,580	$ 23,635
Unamortized debt discount		47,562		47,562
Convertible Senior Notes Maturing February 2026
Debt Instrument [Line Items]
Principal amount	200,000	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%
Maturity date				Feb. 15, 2026
Frequency of periodic payment	semi-annually
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		$ 43,800
Carrying amount of equity component, net of tax		$ 34,600		$ 34,600
Effective interest rate (as a percent)		12.40%		12.40%
Interest expense		$ 2,400		$ 2,400
Unamortized debt discount		43,133		43,133
Convertible Senior Notes Maturing May 2022
Debt Instrument [Line Items]
Principal amount		$ 35,000		$ 35,000		125,000
Repurchase amount	$ 89,100
Repurchased principal amount	90,000
Interest rate (as a percent)		4.25%		4.25%
Maturity date				May 01, 2022
Frequency of periodic payment				semi-annually
Initial conversion ratio				0.0719748
Initial conversion price per share (in dollars per share) | $ / shares		$ 13.89		$ 13.89
Redemption price as a percentage of principal amount				100.00%
Minimum percentage in aggregate principal amount		25.00%		25.00%
Carrying amount of equity component		$ 9,500		$ 9,500		16,900
Carrying amount of equity component, net of tax		$ 5,300		$ 5,300		11,000
Effective interest rate (as a percent)		7.30%		7.30%
Interest expense		$ 1,300	2,100	$ 5,600	6,200
Unamortized debt discount		1,560		1,560		8,000
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Principal amount		$ 30,000		$ 30,000		125,000
Repurchase amount	94,100
Repurchased principal amount	$ 95,000
Interest rate (as a percent)		4.125%		4.125%
Maturity date				Sep. 15, 2023
Frequency of periodic payment				semi-annually
Initial conversion ratio				0.1056133
Initial conversion price per share (in dollars per share) | $ / shares		$ 9.47		$ 9.47
Redemption price as a percentage of principal amount				100.00%
Minimum percentage in aggregate principal amount		25.00%		25.00%
Carrying amount of equity component		$ 4,200		$ 4,200		20,100
Carrying amount of equity component, net of tax		$ 3,600		$ 3,600		15,900
Effective interest rate (as a percent)		7.80%		7.80%
Interest expense		$ 1,300	$ 2,100	$ 5,600	$ 6,300
Unamortized debt discount		$ 2,869		$ 2,869		$ 14,500