Leases (Lease Balances) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
ROU assets recorded during the period associated with:
Finance leases	$ 433.9		$ 531.0
Operating leases	332.0		512.7
Total ROU assets	765.9		1,043.7
Lease liabilities:
Finance lease	532.7		617.1
Operating leases	350.7		545.1
Total lease liabilities	$ 883.4		$ 1,162.2
Weighted average remaining lease term for finance leases	22 years 10 months 24 days
Weighted average discount rate, for finance leases	6.00%
ROU assets associated with finance leases	$ 31.2	$ 47.2
Weighted average remaining lease term for operating leases	7 years 6 months
Weighted average discount rate, for operating leases	3.70%
Addition to ROU assets associated with operating leases	$ 65.8	$ 53.9