Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Supplemental Cash Flow Information [Line Items]
Cash and cash equivalents	$ 220		$ 314
Interest paid	185	$ 144
Income taxes paid	0	1
Increase (decrease) in accounts payable for purchases of property and equipment	7	(18)
Purchase of property and equipment under capital leases and installment purchases	10	9
Restricted Cash, Current	120		121
Restricted Cash, Noncurrent	5		5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	345		$ 440
Preferred Stock [Member]
Supplemental Cash Flow Information [Line Items]
Preferred Stock Dividends Declared, Not Paid	$ 28	$ 0