Railcar Leasing and Management Services Group - Selected consolidating income statement information for the Leasing Group - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Total revenues	$ 906.4	$ 973.6	$ 905.5	$ 877.3	$ 1,103.8	$ 1,111.7	$ 1,184.9	$ 1,187.9	$ 3,662.8	$ 4,588.3	$ 6,392.7
Operating profit:
Total operating profit	$ 144.3	$ 153.0	$ 135.2	$ 116.6	$ 163.6	$ 183.6	$ 191.6	$ 203.4	549.1	742.2	1,438.9
Selected expense information:
Depreciation									295.4	283.0	266.4
Interest:
Interest									184.0	181.9	194.7
Operating Segments
Revenues:
Total revenues									4,662.3	5,935.5	7,978.1
Operating profit:
Total operating profit									815.0	1,052.1	1,852.0
Selected expense information:
Depreciation									285.9	274.4	258.7
Railcar Leasing and Management Services Group
Revenues:
Total revenues									842.2	824.9	1,091.6
Selected expense information:
Depreciation									172.3	156.2	142.3
Railcar Leasing and Management Services Group | Operating Segments
Revenues:
Total revenues									$ 843.2	$ 827.0	1,104.8
Percent Change, Revenues									2.00%	(25.10%)
Operating profit:
Total operating profit									$ 444.5	$ 360.1	$ 606.2
Percentage Change, Operating profit									23.40%	(40.60%)
Operating profit margin:
Total operating profit margin									52.70%	43.50%	54.90%
Selected expense information:
Depreciation									$ 172.3	$ 156.2	$ 142.3
Percent Change, Depreciation									10.30%	9.80%
Maintenance and compliance									$ 96.4	$ 104.3	97.3
Percent Change, Maintenance									(7.60%)	7.20%
Rent									$ 39.9	$ 39.3	41.6
Percent Change, Rent									1.50%	(5.50%)
Interest:
Interest									$ 125.8	$ 125.2	138.8
Percent Change, Total interest expense									0.50%	(9.80%)
Railcar Leasing and Management Services Group | Operating Segments | Leasing and management
Revenues:
Total revenues									$ 743.6	$ 700.9	699.9
Percent Change, Revenues									6.10%	0.10%
Operating profit:
Total operating profit									$ 341.3	$ 312.5	$ 331.1
Percentage Change, Operating profit									9.20%	(5.60%)
Operating profit margin:
Total operating profit margin									45.90%	44.60%	47.30%
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned one year or less at the time of sale
Revenues:
Total revenues									$ 99.6	$ 126.1	$ 404.9
Operating profit:
Total operating profit									19.7	34.1	109.0
Railcar Leasing and Management Services Group | Operating Segments | Railcars owned more than one year at the time of sale
Operating profit:
Total operating profit									$ 83.5	$ 13.5	$ 166.1