Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Supplemental Cash Flow Information [Line Items]
Operating Lease, Payments	[1]	$ 145	$ 0
Interest paid		208	185
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		36	0
Increase (decrease) in accounts payable for purchases of property and equipment		2	7
Purchase of property and equipment under capital leases and installment purchases		9	$ 10
Cash and cash equivalents		245		$ 277
Restricted Cash, Current		158		131
Restricted Cash, Noncurrent		5		5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 408		$ 413

[1] Excludes cash payments related to contingent payment pursuant to operating leases, which are recorded as expense in the period such contingencies are resolved.