Long-Term Debt - Convertible Senior Notes Due 2023 (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) $ / shares	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Interest expense	$ 5,943,000	$ 7,179,000	$ 12,055,000	$ 14,573,000
Amortization of debt issuance costs			$ 1,587,000	1,619,000
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	2,300,000	$ 700,000	4,600,000
Coupon interest expense	$ 300,000	1,300,000	600,000	2,600,000
Amortization of debt issuance costs			$ 100,000
Amortization of debt discount and issuance costs		$ 1,000,000.0		$ 2,000,000.0
Convertible Senior Notes Maturing September 2023 | Minimum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			130.00%
Number of trading days			5
Number of consecutive trading days			10
Convertible Senior Notes Maturing September 2023 | Maximum
Debt Instrument [Line Items]
Percentage of closing price of common stock to conversion price			97.00%
Number of trading days			20
Number of consecutive trading days			30