Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Supplemental Cash Flow Information [Line Items]
Cash payments related to operating lease liabilities	$ 409	$ 0
Interest paid	547	503
Income Taxes Paid	13	15
New ROU assets obtained in exchange for operating lease liabilities	327	0
Increase (decrease) in accounts payable for purchases of property and equipment	17	25
Purchase of property and equipment under capital leases and installment purchases	$ 28	$ 28