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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Revenues	$ 509.2	$ 736.0	$ 1,124.4	$ 1,340.8
Sales-type Lease, Revenue	0.0	32.3	0.0	34.2
Operating profit (loss)(2):
Total operating profit	(307.3)	107.0	(234.3)	198.8
Select expense information:
Depreciation (3)			134.6	138.1
Rent	4.6	4.1	8.5	9.3
Selling, General and Administrative Expense	56.8	69.8	121.1	129.4
Interest	53.0	57.0	114.3	109.7
Leasing [Member]
Revenues:
Revenues	192.6	276.9	428.7	477.1
Select expense information:
Selling, General and Administrative Expense	13.0	12.7	27.3	25.5
Operating Segments [Member]
Revenues:
Revenues	509.2	736.0	1,124.4	1,340.8
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Revenues:
Revenues	$ 192.8	277.1	$ 429.1	477.5
Revenues, Percent Change	(30.40%)		(10.10%)
Operating profit (loss)(2):
Total operating profit	$ 82.9	$ 104.8	$ 175.8	$ 190.6
Operating Income (Loss), Percent Change	(20.90%)		(7.80%)
Operating Profit Margin	43.00%	37.80%	41.00%	39.90%
Select expense information:
Depreciation (3)	$ 54.0	$ 57.8	$ 107.6	$ 112.2
Depreciation, Depletion, and Amortization, Percent Change	(6.60%)		(4.10%)
Maintenance and compliance costs	$ 23.0	26.5	$ 48.9	54.3
Maintenance Costs, Percent Change	(13.20%)		(9.90%)
Rent	$ 3.0	4.3	$ 6.0	9.8
Operating Leases, Rent Expense, Percent Change	(30.20%)		(38.80%)
Selling, General and Administrative Expense	$ 13.0	12.7	$ 27.3	25.5
Selling, Engineering, and Administrative Expense, Percent Change	2.40%		7.10%
Interest	$ 47.1	50.4	$ 102.2	96.4
Interest Expense, Percent Change	(6.50%)		6.00%
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member] | Leasing and Management [Member]
Revenues:
Revenues	$ 182.7	189.4	$ 374.7	376.5
Revenues, Percent Change	(3.50%)		(0.50%)
Operating profit (loss)(2):
Total operating profit	$ 78.5	$ 77.7	$ 161.0	$ 154.8
Operating Income (Loss), Percent Change	1.00%		4.00%
Operating Profit Margin	43.00%	41.00%	43.00%	41.10%
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member] | Railcar Owned One Year or Less [Member]
Revenues:
Revenues	$ 10.1	$ 87.7	$ 54.4	$ 101.0
Revenues, Percent Change	(88.50%)		(46.10%)
Operating profit (loss)(2):
Total operating profit	$ (1.3)	$ 8.4	$ 0.4	$ 9.2
Operating Income (Loss), Percent Change	(115.50%)		(95.70%)
Operating Profit Margin	(12.90%)	9.60%	0.70%	9.10%
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member] | Railcar Owned Greater than One Year [Member]
Operating profit (loss)(2):
Total operating profit	$ 5.7	$ 18.7	$ 14.4	$ 26.6
Operating Income (Loss), Percent Change	(69.50%)		(45.90%)
Operating Profit Margin	8.90%	26.50%	10.90%	26.60%
Service Life [Member]
Select expense information:
Depreciation (3)	$ 7.7		$ 15.4