Leases Lessee, Schedule of Finance Leases (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) tankContainer	Dec. 31, 2021 USD ($) tankContainer	Dec. 31, 2020 USD ($) tankContainer
Lessee, Lease, Description [Line Items]
Finance Lease, Right-of-Use Asset	$ 0.0	$ 1.5
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	0.0	0.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ 177.1	$ 195.1	$ 125.3
Number of railcars received | tankContainer	21	2,329	732
gatxOperatingLeaseOtherIncome	$ 81.5	$ 74.8	$ 88.9
Railcars [Member]
Lessee, Lease, Description [Line Items]
Finance Lease, Right-of-Use Asset, before Accumulated Amortization	$ 0.0	$ 1.5