Debt and Financing Obligation - Schedule of Debt (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total borrowings	$ 739,900,000	$ 800,500,000
Original issue discount	(3,700,000)	(4,300,000)
Debt issuance costs	(11,400,000)	(13,300,000)
Total debt and financing obligation	724,800,000	782,900,000
Less: current portion of financing obligation	5,100,000	2,900,000
Long-term debt and financing obligation	719,700,000	780,000,000.0
7.50 percent senior notes, due 2025 ("2025 Senior Notes") | Senior notes
Debt Instrument [Line Items]
Total borrowings	$ 630,500,000	650,000,000.0
Interest rate on senior notes (as a percent)	7.50%
$400.0 million revolving credit facility, due 2024 ("Revolving Facility") | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Total borrowings	$ 104,300,000	143,300,000
Maximum borrowing capacity	400,000,000.0
5.82 percent financing obligation, due 2021 ("Financing Obligation") | Financing Obligation
Debt Instrument [Line Items]
Total borrowings	$ 5,100,000	$ 7,200,000
Interest rate on senior notes (as a percent)	5.82%