Leases (Lease Balances) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
ROU assets recorded during the period associated with:
Finance leases	$ 439.2		$ 471.6
Operating leases	1,315.4		1,440.3
Total ROU assets	1,754.6		1,911.9
Lease liabilities:
Finance lease	493.2		549.5
Operating leases	1,323.6		1,432.0
Total lease liabilities	$ 1,816.8		$ 1,981.5
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property and equipment, net		Property and equipment, net
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets, net		Other assets, net
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term debt and finance lease obligations		Long-term debt and finance lease obligations
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current portion of debt and finance lease obligations (notes 9 and 10)		Current portion of debt and finance lease obligations (notes 9 and 10)
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Accrued Liabilities, Current		Other Accrued Liabilities, Current
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other Liabilities, Noncurrent		Other Liabilities, Noncurrent
Weighted average remaining lease term for finance leases	22 years 7 months 6 days
Weighted average discount rate, for finance leases	6.00%
ROU assets associated with finance leases	$ 27.8	$ 30.9
Weighted average remaining lease term for operating leases	11 years 7 months 6 days
Weighted average discount rate, for operating leases	5.80%
Addition to ROU assets associated with operating leases	$ 67.4	$ 64.2