Railcar Leasing and Management Services Group - Selected consolidating financial information for the Leasing Group (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Receivables, net of allowance	$ 226.9	$ 260.1
Property, Plant and Equipment, Net	6,784.4	7,110.6
Restricted Cash and Cash Equivalents	136.9	111.4
Other assets	266.9	396.2
Assets	8,665.4	8,701.4
Recourse And Non-Recourse Debt And Capital Lease Obligations	4,825.4	4,881.9
Other liabilities	139.4	96.3
Liabilities	6,505.0	6,322.5
Noncontrolling interest	269.1	348.8
Stockholders' Equity Attributable to Parent	1,891.3	2,030.1
Operating Segments [Member] | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash, Cash Equivalents, and Short-term Investments	2.9	1.8
Receivables, net of allowance	86.4	82.6
Property, Plant and Equipment, Net	7,205.3	7,605.6
Restricted Cash and Cash Equivalents	136.9	111.4
Other assets	38.6	211.2
Assets	7,470.1	8,012.6
Accounts Payable and Accrued Liabilities	185.3	145.3
Recourse And Non-Recourse Debt And Capital Lease Obligations	4,297.4	4,359.1
Deferred Tax Liabilities, Net	923.8	862.8
Other liabilities	29.0	32.7
Liabilities	5,435.5	5,399.9
Noncontrolling interest	269.1	348.8
Stockholders' Equity Attributable to Parent	1,765.5	2,263.9
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	(832.6)	(903.8)
Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash, Cash Equivalents, and Short-term Investments	2.9	1.8
Receivables, net of allowance	86.4	82.6
Property, Plant and Equipment, Net	6,372.7	6,701.8
Restricted Cash and Cash Equivalents	136.9	111.4
Other assets	38.6	211.2
Assets	6,637.5	7,108.8
Accounts Payable and Accrued Liabilities	185.3	145.3
Recourse And Non-Recourse Debt And Capital Lease Obligations	4,297.4	4,359.1
Deferred Tax Liabilities, Net	728.6	678.0
Other liabilities	29.0	32.7
Liabilities	5,240.3	5,215.1
Noncontrolling interest	269.1	348.8
Stockholders' Equity Attributable to Parent	1,128.1	1,544.9
Wholly-owned subsidiaries | Operating Segments [Member] | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash, Cash Equivalents, and Short-term Investments	2.9	1.8
Receivables, net of allowance	77.2	73.9
Property, Plant and Equipment, Net	5,557.1	5,818.9
Restricted Cash and Cash Equivalents	109.2	78.4
Other assets	37.3	209.8
Assets	5,783.7	6,182.8
Accounts Payable and Accrued Liabilities	145.0	100.7
Recourse And Non-Recourse Debt And Capital Lease Obligations	3,045.7	3,080.7
Deferred Tax Liabilities, Net	922.6	861.7
Other liabilities	29.0	32.7
Liabilities	4,142.3	4,075.8
Noncontrolling interest	0.0	0.0
Stockholders' Equity Attributable to Parent	1,641.4	2,107.0
Partially-owned subsidiaries | Operating Segments [Member] | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash, Cash Equivalents, and Short-term Investments	0.0	0.0
Receivables, net of allowance	9.2	8.7
Property, Plant and Equipment, Net	1,648.2	1,786.7
Restricted Cash and Cash Equivalents	27.7	33.0
Other assets	1.3	1.4
Assets	1,686.4	1,829.8
Accounts Payable and Accrued Liabilities	40.3	44.6
Recourse And Non-Recourse Debt And Capital Lease Obligations	1,251.7	1,278.4
Deferred Tax Liabilities, Net	1.2	1.1
Other liabilities	0.0	0.0
Liabilities	1,293.2	1,324.1
Noncontrolling interest	269.1	348.8
Stockholders' Equity Attributable to Parent	124.1	156.9
Consolidated Subsidiaries, Leasing [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Cash, Cash Equivalents, and Short-term Investments	0.0	0.0
Receivables, net of allowance	0.0	0.0
Property, Plant and Equipment, Net	(832.6)	(903.8)
Restricted Cash and Cash Equivalents	0.0	0.0
Other assets	0.0	0.0
Assets	(832.6)	(903.8)
Accounts Payable and Accrued Liabilities	0.0	0.0
Recourse And Non-Recourse Debt And Capital Lease Obligations	0.0	0.0
Deferred Tax Liabilities, Net	(195.2)	(184.8)
Other liabilities	0.0	0.0
Liabilities	(195.2)	(184.8)
Noncontrolling interest	0.0	0.0
Stockholders' Equity Attributable to Parent	$ (637.4)	$ (719.0)