Leases (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) railcar	Dec. 31, 2022 USD ($) tankContainer	Dec. 31, 2021 USD ($) tankContainer
Operating Leased Assets [Line Items]
Number of railcars received | tankContainer		21	2,329
Lessee, Lease, Number of Railcars Leased | railcar	5,162
Direct Financing Lease, Lease Income	$ 12.6	$ 9.8	$ 7.0
Operating Lease, Lease Income, Lease Payments	1,145.1	1,058.3	1,063.4
Operating Lease, Variable Lease Income	93.7	86.5	70.1
Operating Lease, Lease Income	1,238.8	1,144.8	1,133.5
Lease Income	1,251.4	1,154.6	$ 1,140.5
Total contractual lease payments receivable	171.8	110.4
Estimated unguaranteed residual value of leased assets	17.2	18.1
Unearned income	(52.6)	(32.0)
Finance leases	$ 136.4	$ 96.5