Railcar Leasing and Management Services Group - Selected consolidating financial information for the Leasing Group (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Receivables, net of allowance	$ 297.8	$ 260.1
Property, plant, and equipment, net	7,118.7	7,110.6
Restricted cash	96.3	111.4
Other assets	237.0	396.2
Assets	9,002.9	8,701.4
Recourse And Non-Recourse Debt And Capital Lease Obligations	4,870.2	4,881.9
Other liabilities	93.5	96.3
Liabilities	6,536.8	6,322.5
Noncontrolling interest	349.7	348.8
Stockholders' Equity Attributable to Parent	2,116.4	2,030.1
Operating Segments | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash and cash equivalents	7.3	1.8
Receivables, net of allowance	85.0	82.6
Property, plant, and equipment, net	7,614.1	7,605.6
Restricted cash	96.3	111.4
Other assets	54.7	211.2
Assets	7,857.4	8,012.6
Accounts Payable and Accrued Liabilities	128.0	117.3
Recourse And Non-Recourse Debt And Capital Lease Obligations	4,342.3	4,359.1
Deferred Tax Liabilities, Net	913.5	862.8
Other liabilities	82.7	60.7
Liabilities	5,466.5	5,399.9
Noncontrolling interest	349.7	348.8
Stockholders' Equity Attributable to Parent	2,041.2	2,263.9
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Property, plant, and equipment, net	(899.7)	(903.8)
Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash and cash equivalents	7.3	1.8
Receivables, net of allowance	85.0	82.6
Property, plant, and equipment, net	6,714.4	6,701.8
Restricted cash	96.3	111.4
Other assets	54.7	211.2
Assets	6,957.7	7,108.8
Accounts Payable and Accrued Liabilities	128.0	117.3
Recourse And Non-Recourse Debt And Capital Lease Obligations	4,342.3	4,359.1
Deferred Tax Liabilities, Net	710.6	678.0
Other liabilities	82.7	60.7
Liabilities	5,263.6	5,215.1
Noncontrolling interest	349.7	348.8
Stockholders' Equity Attributable to Parent	1,344.4	1,544.9
Wholly-owned subsidiaries | Operating Segments | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash and cash equivalents	7.3	1.8
Receivables, net of allowance	75.7	73.9
Property, plant, and equipment, net	5,837.5	5,818.9
Restricted cash	69.0	78.4
Other assets	53.4	209.8
Assets	6,042.9	6,182.8
Accounts Payable and Accrued Liabilities	85.6	72.7
Recourse And Non-Recourse Debt And Capital Lease Obligations	3,078.8	3,080.7
Deferred Tax Liabilities, Net	912.4	861.7
Other liabilities	82.7	60.7
Liabilities	4,159.5	4,075.8
Noncontrolling interest	0.0	0.0
Stockholders' Equity Attributable to Parent	1,883.4	2,107.0
Partially-owned subsidiaries
Segment Reporting Information [Line Items]
Restricted cash	27.3	33.0
Partially-owned subsidiaries | Operating Segments | Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
Cash and cash equivalents	0.0	0.0
Receivables, net of allowance	9.3	8.7
Property, plant, and equipment, net	1,776.6	1,786.7
Restricted cash		33.0
Other assets	1.3	1.4
Assets	1,814.5	1,829.8
Accounts Payable and Accrued Liabilities	42.4	44.6
Recourse And Non-Recourse Debt And Capital Lease Obligations	1,263.5	1,278.4
Deferred Tax Liabilities, Net	1.1	1.1
Other liabilities	0.0	0.0
Liabilities	1,307.0	1,324.1
Noncontrolling interest	349.7	348.8
Stockholders' Equity Attributable to Parent	157.8	156.9
Consolidated Subsidiaries, Leasing [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Cash and cash equivalents	0.0	0.0
Receivables, net of allowance	0.0	0.0
Property, plant, and equipment, net	(899.7)	(903.8)
Restricted cash	0.0	0.0
Other assets	0.0	0.0
Assets	(899.7)	(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	(202.9)	(184.8)
Other liabilities	0.0	0.0
Liabilities	(202.9)	(184.8)
Noncontrolling interest	0.0	0.0
Stockholders' Equity Attributable to Parent	$ (696.8)	$ (719.0)