Commitments and Contingent Liabilities, Consolidated Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Consolidated Lease Expense [Abstract]
Non-cash lease expense (amortization of ROU assets)	$ 9.3	$ 9.8	$ 18.6	$ 19.8
Related accretion expense on lease liability balances	3.0	3.3	6.1	6.7
Total fixed lease expense	12.3	13.1	24.7	26.5
Variable lease expense	0.2	0.1	0.6	0.3
Subtotal operating lease expense	12.5	13.2	25.3	26.8
Short-term operating leases	12.9	11.8	26.4	25.0
Total operating lease expense	25.4	25.0	51.7	51.8
Cash payments for operating lease liabilities	9.3	7.9	18.4	18.3
Operating lease income	$ 3.1	$ 2.6	$ 6.1	$ 6.1