Leases (Lease Balances) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term for operating leases	8 years
Weighted average discount rate for operating leases	4.00%
Weighted average remaining lease term for finance leases	23 years 7 months 6 days
Weighted average discount rate for finance leases	6.00%
Operating leases	$ 518.4
Finance leases	557.4
Total	1,075.8
ROU assets recorded during the period associated with:
Operating leases	3.5
Finance leases	12.2
Total	15.7
ROU assets associated with finance leases additions	698.6	$ 983.6
Operating leases	525.4
Finance lease obligations (note 10)	631.5
Total	1,156.9
Finance lease obligations (note 10)			$ 621.3
Assets Held under Capital Leases
ROU assets recorded during the period associated with:
ROU assets associated with finance leases additions	$ 23.9