Summary of Significant Accounting Policies Lessee Accounting (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Renewal Term		5 years
Lessee, Operating Lease, Termination Option Term		one year
Finance Lease, Principal Payments		$ 0.0
Operating lease expense		3.7	$ 3.9
Short-term lease expense		0.0	0.2
Right-of-use assets (1)	[1]	86.9		$ 77.1
Lease liabilities (2)	[2]	$ 110.2		$ 96.9
Weighted average remaining lease term		10 years 10 months 24 days		11 years 3 months 18 days
Weighted average discount rate		3.10%		3.30%
Cash flows from operating activities		$ 3.7	3.9
Right-of-use assets recognized in exchange for new lease liabilities		13.8	$ 2.1
Remaining nine months of 2021		10.7
2022		17.3
2023		15.7
2024		11.2
2025		8.6
Thereafter		68.6
Total operating lease payments		132.1
Less: Present value adjustment		$ (21.9)
Minimum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract		1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract		16 years
Railcar Leasing and Management Services Group [Member]
Lessee, Lease, Description [Line Items]
Remaining nine months of 2021		$ 7.6
2022		9.3
2023		7.6
2024		4.3
2025		2.4
Thereafter		3.8
Total operating lease payments		35.0
Consolidated Subsidiaries, Excluding Leasing [Member]
Lessee, Lease, Description [Line Items]
Remaining nine months of 2021		3.1
2022		8.0
2023		8.1
2024		6.9
2025		6.2
Thereafter		64.8
Total operating lease payments		$ 97.1

[1] Included in other assets in our Consolidated Balance Sheet.

[2] Included in other liabilities in our Consolidated Balance Sheet.