Long-Term Debt - Summary of Long Term Debt (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Summary of Long-term debt
MRL term loan credit agreement		$ 74.3	$ 74.4
Asset financing arrangement		48.9	50.8
MRL asset financing arrangements		380.6	384.6
Present value of lease liabilities		2.7	3.0
Less unamortized debt issuance costs	[1]	(17.4)	(16.1)
Less unamortized discounts		(3.1)	(3.5)
Total debt		2,081.9	1,885.4
Less current portion of long-term debt		26.3	55.7
Total long-term debt		2,055.6	1,829.7
Accumulated amortization, deferred debt issuance costs		27.8	26.6
Revolving Credit Facility
Summary of Long-term debt
Long-term line of credit		309.8	136.7
MRL Revolving Credit Agreement
Summary of Long-term debt
Borrowings under senior notes		22.6	13.0
9.25% Senior Notes due July 2024
Summary of Long-term debt
Borrowings under senior notes			179.0
11.00% Senior Notes due 2025
Summary of Long-term debt
Borrowings under senior notes		413.5	413.5
8.125% Senior Notes due July 2027
Summary of Long-term debt
Borrowings under senior notes		325.0	325.0
9.75% July 2028, Notes
Summary of Long-term debt
Borrowings under senior notes		325.0	$ 325.0
9.25% Senior Secured First Lien Notes due 2029 (the "2029 Secured Notes")
Summary of Long-term debt
Borrowings under senior notes		$ 200.0

[1] Deferred debt issuance costs are being amortized by the effective interest rate method over the lives of the related debt instruments. These amounts are net of accumulated amortization of $27.8 million and $26.6 million at March 31, 2024 and December 31, 2023, respectively.