Railcar Leasing and Management Services Group - Selected consolidating income statement information for the Leasing Group (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Revenues	$ 736.0	$ 634.0	$ 1,340.8	$ 1,167.2
Sales-type Lease, Revenue	32.3		34.2
Operating profit:
Total operating profit	107.0	88.0	198.8	150.1
Select expense information:
Depreciation			138.1	119.7
Rent	4.1		9.3
Selling, General and Administrative Expense	69.8	75.6	129.4	149.0
Interest	57.0	43.8	109.7	90.1
Leasing [Member]
Revenues:
Revenues	276.9	213.2	477.1	387.5
Select expense information:
Selling, General and Administrative Expense	12.7	12.6	25.5	24.8
Operating Segments
Revenues:
Revenues	736.0	634.0	1,340.8	1,167.2
Railcar Leasing and Management Services Group | Operating Segments
Revenues:
Revenues	$ 277.1	213.4	$ 477.5	388.0
Revenues, Percent Change	29.90%		23.10%
Operating profit:
Total operating profit	$ 104.8	$ 91.8	$ 190.6	$ 162.9
Operating Income (Loss), Percent Change	14.20%		17.00%
Total operating profit margin	37.80%	43.00%	39.90%	42.00%
Select expense information:
Depreciation	$ 57.8	$ 47.0	$ 112.2	$ 92.1
Depreciation, Depletion, and Amortization, Percent Change	23.00%		21.80%
Maintenance and compliance costs	$ 26.5	25.0	$ 54.3	51.4
Maintenance Costs, Percent Change	6.00%		5.60%
Rent	$ 4.3	9.9	$ 9.8	20.0
Operating Leases, Rent Expense, Percent Change	(56.60%)		(51.00%)
Selling, General and Administrative Expense	$ 12.7	12.6	$ 25.5	24.8
Selling, Engineering, and Administrative Expense, Percent Change	0.80%		2.80%
Interest	$ 50.4	32.3	$ 96.4	63.8
Interest Expense, Percent Change	56.00%		51.10%
Railcar Leasing and Management Services Group | Operating Segments | Leasing and management
Revenues:
Revenues	$ 189.4	184.2	$ 376.5	358.8
Revenues, Percent Change	2.80%		4.90%
Operating profit:
Total operating profit	$ 77.7	$ 77.9	$ 154.8	$ 146.9
Operating Income (Loss), Percent Change	(0.30%)		5.40%
Total operating profit margin	41.00%	42.30%	41.10%	40.90%
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned one year or less at the time of sale
Revenues:
Revenues	$ 87.7	$ 29.2	$ 101.0	$ 29.2
Operating profit:
Total operating profit	8.4	4.4	9.2	4.4
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned more than one year at the time of sale
Operating profit:
Total operating profit	$ 18.7	$ 9.5	$ 26.6	$ 11.6