Railcar Leasing and Management Services Group - Schedule of proceeds from leased railcars (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	$ 204.2	$ 254.0
Railcar Leasing and Management Services Group | Railcars owned one year or less at the time of sale
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	80.8	93.7
Railcar Leasing and Management Services Group | Railcars owned more than one year at the time of sale
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	$ 123.4	$ 160.3