Railcar Leasing and Management Services Group - Selected consolidating income statement information for the Leasing Group (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues:
Revenues	$ 615.2	$ 604.8
Sales-type Lease, Revenue	0.0
Operating profit(1):
Total operating profit	73.0	91.8
Select expense information:
Depreciation (2)	66.9	67.5
Rent	3.9	5.2
Selling, General and Administrative Expense	64.3	59.6
Interest	61.3	52.7
Leasing [Member]
Revenues:
Revenues	236.1	200.2
Select expense information:
Selling, General and Administrative Expense	14.3	12.8
Operating Segments
Revenues:
Revenues	615.2	604.8
Railcar Leasing and Management Services Group | Operating Segments
Revenues:
Revenues	$ 236.3	200.4
Revenues, Percent Change	17.90%
Operating profit(1):
Total operating profit	$ 92.9	$ 85.8
Operating Income (Loss), Percent Change	8.30%
Total operating profit margin	39.30%	42.80%
Select expense information:
Depreciation (2)	$ 53.6	$ 54.4
Depreciation, Depletion, and Amortization, Percent Change	(1.50%)
Maintenance and compliance costs	$ 25.9	27.8
Maintenance Costs, Percent Change	(6.80%)
Rent	$ 3.0	5.5
Operating Leases, Rent Expense, Percent Change	(45.50%)
Selling, General and Administrative Expense	$ 14.3	12.8
Selling, Engineering, and Administrative Expense, Percent Change	11.70%
Interest	$ 55.1	46.0
Interest Expense, Percent Change	19.80%
Railcar Leasing and Management Services Group | Operating Segments | Leasing and management
Revenues:
Revenues	$ 192.0	187.1
Revenues, Percent Change	2.60%
Operating profit(1):
Total operating profit	$ 82.5	$ 77.1
Operating Income (Loss), Percent Change	7.00%
Total operating profit margin	43.00%	41.20%
Railcar Leasing and Management Services Group | Operating Segments | Railcar Owned One Year or Less [Member]
Revenues:
Revenues	$ 44.3	$ 13.3
Revenues, Percent Change	233.10%
Operating profit(1):
Total operating profit	$ 1.7	$ 0.8
Operating Income (Loss), Percent Change	112.50%
Total operating profit margin	3.80%	6.00%
Railcar Leasing and Management Services Group | Operating Segments | Railcar Owned Greater than One Year [Member]
Operating profit(1):
Total operating profit	$ 8.7	$ 7.9
Operating Income (Loss), Percent Change	10.10%
Total operating profit margin	12.70%	26.90%
Service Life [Member]
Select expense information:
Depreciation (2)	$ 7.7