Summary of Significant Accounting Policies Lessor Accounting (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Renewal Term	5 years	5 years
Lessor, Operating Lease, Termination Option Term		1 year
Direct Financing Lease, Revenue		$ 0.0
Operating Lease, Lease Income, Lease Payments	$ 171.6	339.9
Operating Lease, Variable Lease Income	10.8	21.6
Sales-type Lease, Revenue	32.3	34.2
Sales-type Lease, Interest Income	0.3	0.3
Sales-type Lease, Selling Profit (Loss)	3.9	4.1
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Remainder of Fiscal Year	5.3	5.3
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Two Years	9.0	9.0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Three Years	24.9	24.9
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Four Years	0.0	0.0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Five Years	0.0	0.0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Thereafter	0.0	0.0
Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received	39.2	39.2
Sales-type and Direct Financing Leases, Lease Receivable, Undiscounted Excess Amount	(4.7)	(4.7)
Sales-type Lease, Net Investment in Lease	34.5	34.5
Net Investment in Lease, Current	1.1	1.1
Net Investment in Lease, Noncurrent	33.4	33.4
Railcar Leasing and Management Services Group [Member]
Lessor, Lease, Description [Line Items]
Operating Leases, Future Minimum Payments Receivable, Remainder of Fiscal Year	295.6	295.6
Operating Leases, Future Minimum Payments Receivable, in Two Years	504.3	504.3
Operating Leases, Future Minimum Payments Receivable, in Three Years	390.1	390.1
Operating Leases, Future Minimum Payments Receivable, in Four Years	293.8	293.8
Operating Leases, Future Minimum Payments Receivable, in Five Years	198.6	198.6
Operating Leases, Future Minimum Payments Receivable, Thereafter	355.9	355.9
Operating Leases, Future Minimum Payments Receivable	$ 2,038.3	$ 2,038.3
Minimum | Railcar Leasing and Management Services Group [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Term of Contract	1 year	1 year
Maximum | Railcar Leasing and Management Services Group [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Term of Contract	10 years	10 years	20 years