Railcar Leasing and Management Services Group - Selected consolidating income statement information for the Leasing Group (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Revenues	$ 604.8	$ 533.2
Operating profit:
Total operating profit	91.8	62.1
Select expense information:
Depreciation	67.5	58.2
Rent	5.2
Selling, General and Administrative Expense	59.6	73.4
Interest	52.7	46.3
Leasing [Member]
Revenues:
Revenues	200.2	174.3
Select expense information:
Selling, General and Administrative Expense	12.8	12.2
Operating Segments
Revenues:
Revenues	604.8	533.2
Railcar Leasing and Management Services Group | Operating Segments
Revenues:
Revenues	$ 200.4	174.6
Revenues, Percent Change	14.80%
Operating profit:
Total operating profit	$ 85.8	$ 71.1
Operating Income (Loss), Percent Change	20.70%
Total operating profit margin	42.80%	40.70%
Select expense information:
Depreciation	$ 54.4	$ 45.1
Depreciation, Depletion, and Amortization, Percent Change	20.60%
Maintenance and compliance costs	$ 27.8	26.4
Maintenance Costs, Percent Change	5.30%
Rent	$ 5.5	10.1
Operating Leases, Rent Expense, Percent Change	(45.50%)
Selling, General and Administrative Expense	$ 12.8	12.2
Selling, Engineering, and Administrative Expense, Percent Change	4.90%
Interest	$ 46.0	31.5
Interest Expense, Percent Change	46.00%
Railcar Leasing and Management Services Group | Operating Segments | Leasing and management
Revenues:
Revenues	$ 187.1	174.6
Revenues, Percent Change	7.20%
Operating profit:
Total operating profit	$ 77.1	$ 69.0
Operating Income (Loss), Percent Change	11.70%
Total operating profit margin	41.20%	39.50%
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned one year or less at the time of sale
Revenues:
Revenues	$ 13.3	$ 0.0
Operating profit:
Total operating profit	0.8	0.0
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned more than one year at the time of sale
Operating profit:
Total operating profit	$ 7.9	$ 2.1