Fair Value Measurements - Carrying Value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions
MRL term loan credit agreement	$ 74.6
Asset financing arrangement	52.7	$ 58.2
MRL asset financing arrangements	388.0	370.1
Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes payable, fair value disclosure	1,232.4	1,045.2
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
MRL term loan credit agreement	74.6	0.0
Asset financing arrangement	52.7	58.2
Oaktree credit agreement		0.0
MRL asset financing arrangements	388.0	370.1
Debt instrument, fair value disclosure	3.0	3.4
Fair Value | Level 3 | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Lines of credit, fair value disclosure	71.1	104.0
Carrying Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes payable, fair value disclosure	1,231.3	1,030.0
Carrying Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
MRL revolving credit agreement	(0.6)
MRL term loan credit agreement	71.7
Asset financing arrangement	52.0	57.2
Oaktree credit agreement		(0.6)
MRL asset financing arrangements	386.8	368.8
Debt instrument, fair value disclosure	3.0	3.4
Carrying Value | Level 3 | Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Lines of credit, fair value disclosure	$ 68.6	$ 100.9