Long-Term Debt - Convertible Senior Notes Due 2023 (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Interest expense	$ 6,097,000	$ 8,007,000	$ 18,152,000	$ 22,580,000
Amortization of debt issuance costs			$ 2,596,000	2,401,000
Convertible Senior Notes Maturing September 2023
Debt Instrument [Line Items]
Interest rate (as a percent)	4.125%		4.125%
Frequency of periodic payment			semi-annually
Maturity date			Sep. 15, 2023
Initial conversion ratio			0.1056133
Aggregate number of shares | shares			3,168,399
Initial conversion price per share (USD per share) | $ / shares	$ 9.47		$ 9.47
Increase in the conversion rate			0.0475260
Redemption price as a percentage of principal amount			100.00%
Unamortized debt discount and debt issuance costs					$ 3,100,000
Unamortized debt issuance costs	$ 400,000		$ 400,000
Effective interest rate (as a percent)	4.80%		4.80%		7.80%
Interest expense	$ 300,000	1,400,000	$ 1,000,000.0	6,000,000.0
Coupon interest expense	$ 300,000	800,000	900,000	3,400,000
Amortization of debt issuance costs			$ 100,000
Amortization of debt discount and issuance costs		$ 600,000		$ 2,600,000
Convertible Senior Notes Maturing September 2023 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			20
Number of consecutive trading days			30
Convertible Senior Notes Maturing September 2023 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			5
Number of consecutive trading days			10