Railcar Leasing and Management Services Group - Selected consolidating income statement information for the Leasing Group (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Revenues	$ 813.6	$ 606.9	$ 2,154.4	$ 1,774.1
Sales-type Lease, Revenue	26.3		60.5
Operating profit(2):
Total operating profit	120.3	75.2	319.1	225.3
Select expense information:
Depreciation			210.5	184.3
Rent	4.0		13.3
Selling, General and Administrative Expense	62.1	75.6	191.5	224.6
Interest	55.8	42.8	165.5	132.9
Leasing [Member]
Revenues:
Revenues	326.2	227.2	803.3	614.7
Select expense information:
Selling, General and Administrative Expense	10.7	11.9	36.2	36.7
Operating Segments
Revenues:
Revenues	813.6	606.9	2,154.4	1,774.1
Railcar Leasing and Management Services Group | Operating Segments
Revenues:
Revenues	$ 326.4	227.5	$ 803.9	615.5
Revenues, Percent Change	43.50%		30.60%
Operating profit(2):
Total operating profit	$ 115.7	$ 92.2	$ 306.3	$ 255.1
Operating Income (Loss), Percent Change	25.50%		20.10%
Total operating profit margin	35.40%	40.50%	38.10%	41.40%
Select expense information:
Depreciation	$ 59.4	$ 48.8	$ 171.6	$ 140.9
Depreciation, Depletion, and Amortization, Percent Change	21.70%		21.80%
Maintenance and compliance costs	$ 24.9	24.1	$ 79.2	75.5
Maintenance Costs, Percent Change	3.30%		4.90%
Rent	$ 3.8	9.7	$ 13.6	29.7
Operating Leases, Rent Expense, Percent Change	(60.80%)		(54.20%)
Selling, General and Administrative Expense	$ 10.7	11.9	$ 36.2	36.7
Selling, Engineering, and Administrative Expense, Percent Change	(10.10%)		(1.40%)
Interest	$ 50.0	37.4	$ 146.4	101.2
Interest Expense, Percent Change	33.70%		44.70%
Railcar Leasing and Management Services Group | Operating Segments | Leasing and management
Revenues:
Revenues	$ 190.1	175.9	$ 566.6	534.7
Revenues, Percent Change	8.10%		6.00%
Operating profit(2):
Total operating profit	$ 79.8	$ 69.7	$ 234.6	$ 216.6
Operating Income (Loss), Percent Change	14.50%		8.30%
Total operating profit margin	42.00%	39.60%	41.40%	40.50%
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned one year or less at the time of sale
Revenues:
Revenues	$ 136.3	$ 51.6	$ 237.3	$ 80.8
Operating profit(2):
Total operating profit	17.8	13.1	27.0	17.5
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned more than one year at the time of sale
Operating profit(2):
Total operating profit	$ 18.1	$ 9.4	$ 44.7	$ 21.0