Financial Data of Business Segments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) Segment AircraftEngines	Mar. 31, 2021 USD ($) AircraftEngines	Dec. 31, 2021 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income	$ 75.8	$ 36.5
Provision for Income Taxes, Equity Method Investment	(1.2)	1.8
Lease Income	283.3	280.6
Marine operating revenue	6.2	3.6
Other Operating Income	27.1	21.6
Total Revenues	316.6	305.8
Cost of Property Repairs and Maintenance	74.6	74.3
Marine operating expense	4.2	4.6
Depreciation	89.5	88.6
Operating Lease, Expense	9.1	10.9
Other operating expense	10.7	10.2
Total Expenses	188.1	188.6
Gain (Loss) on Disposition of Assets, Net	73.7	22.5
Interest expense, net	(51.2)	(53.6)
Other (expense) income	(2.0)	(1.3)
Share of affiliates' earnings (pre-tax)	(4.8)	9.0
Segment profit (loss)	144.2	93.8
Income tax benefit	22.4	8.4
Selling, general and administrative	47.2	47.1
Disposition Gains on Owned Assets	64.9	16.3
Nonoperating Income, Residual Sharing Income	2.9	0.7
Nonremarketing Disposition Gain (Loss)	5.9	5.5
Portfolio Investments and Capital Additions	370.4	509.5
Identifiable assets	9,908.6
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	585.0		$ 588.4
Assets	$ 9,908.6		9,541.7
Number of business segments | Segment	3
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	$ 21.2	10.2
Other Business Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	6.7	3.6
Marine operating revenue	0.0	0.0
Other Operating Income	1.8	1.1
Total Revenues	8.5	4.7
Cost of Property Repairs and Maintenance	0.7	0.5
Marine operating expense	0.0	0.0
Depreciation	3.0	1.9
Operating Lease, Expense	0.0	0.0
Other operating expense	0.5	0.4
Total Expenses	4.2	2.8
Gain (Loss) on Disposition of Assets, Net	0.2	0.1
Interest expense, net	(0.9)	(1.3)
Other (expense) income	(0.8)	(0.5)
Share of affiliates' earnings (pre-tax)	0.0	0.0
Segment profit (loss)	2.8	0.2
Disposition Gains on Owned Assets	0.1	0.0
Nonoperating Income, Residual Sharing Income	0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.1	0.1
Portfolio Investments and Capital Additions	11.1	3.5
Identifiable assets	921.0
Assets			621.4
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	200.7	206.8
Marine operating revenue	0.0	0.0
Other Operating Income	23.0	17.8
Total Revenues	223.7	224.6
Cost of Property Repairs and Maintenance	59.9	58.4
Marine operating expense	0.0	0.0
Depreciation	63.5	65.7
Operating Lease, Expense	9.1	10.9
Other operating expense	7.3	7.6
Total Expenses	139.8	142.6
Gain (Loss) on Disposition of Assets, Net	71.6	21.5
Interest expense, net	(34.4)	(37.0)
Other (expense) income	(0.7)	(0.8)
Share of affiliates' earnings (pre-tax)	0.0	0.0
Segment profit (loss)	120.4	65.7
Disposition Gains on Owned Assets	64.4	16.3
Nonoperating Income, Residual Sharing Income	2.0	0.1
Nonremarketing Disposition Gain (Loss)	5.2	5.1
Portfolio Investments and Capital Additions	280.4	109.1
Identifiable assets	6,228.4
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.3		0.3
Assets			6,141.7
Rail International [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	67.6	66.9
Marine operating revenue	0.0	0.0
Other Operating Income	2.3	2.5
Total Revenues	69.9	69.4
Cost of Property Repairs and Maintenance	14.0	15.4
Marine operating expense	0.0	0.0
Depreciation	18.0	18.3
Operating Lease, Expense	0.0	0.0
Other operating expense	2.4	2.0
Total Expenses	34.4	35.7
Gain (Loss) on Disposition of Assets, Net	1.0	0.3
Interest expense, net	(11.2)	(12.2)
Other (expense) income	(0.4)	0.0
Share of affiliates' earnings (pre-tax)	0.0	0.0
Segment profit (loss)	24.9	21.8
Disposition Gains on Owned Assets	0.4	0.0
Nonoperating Income, Residual Sharing Income	0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.6	0.3
Portfolio Investments and Capital Additions	78.9	44.4
Identifiable assets	1,719.1
Assets			1,729.9
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8.3	3.3
Marine operating revenue	6.2	3.6
Other Operating Income	0.0	0.2
Total Revenues	14.5	7.1
Cost of Property Repairs and Maintenance	0.0	0.0
Marine operating expense	4.2	4.6
Depreciation	5.0	2.7
Operating Lease, Expense	0.0	0.0
Other operating expense	0.5	0.2
Total Expenses	9.7	7.5
Gain (Loss) on Disposition of Assets, Net	0.9	0.6
Interest expense, net	(4.7)	(3.1)
Other (expense) income	(0.1)	0.0
Share of affiliates' earnings (pre-tax)	(4.8)	9.0
Segment profit (loss)	(3.9)	6.1
Disposition Gains on Owned Assets	0.0	0.0
Nonoperating Income, Residual Sharing Income	0.9	0.6
Nonremarketing Disposition Gain (Loss)	0.0	0.0
Portfolio Investments and Capital Additions	0.0	$ 352.5
Identifiable assets	1,040.1
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 584.7		588.1
Assets			$ 1,048.7
Number of aircraft engines | AircraftEngines		14
Number of Specialized Gas Vessels | AircraftEngines	5
Portfolio Management | Rolls-Royce Aircraft Engines
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payments to Acquire Property, Plant, and Equipment		$ 352.0