Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flows from Operating Activities:
Net Income	$ 406	$ 427
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	983	930
Non-cash compensation expense attributable to stock awards	120	121
Loss on modification and extinguishment of debt	44	40
Accretion of debt discount and amortization of debt issuance costs	13	15
Accrued interest on long-term debt, net	(34)	27
Deferred income taxes	189	163
Loss (gain) on sale of property, plant and equipment and other assets	6	(1)
Other, net	5	(7)
Changes in working capital items:
Receivables	(34)	16
Other current assets	(38)	(40)
Accounts payable	(10)	99
Deferred revenue	134	21
Other current liabilities	7	(25)
Net Cash Provided by Operating Activities	1,791	1,786
Cash Flows from Investing Activities:
Capital expenditures	(1,018)	(1,028)
Change in restricted cash and securities, net	4	11
Purchases of marketable securities	(1,127)	0
Maturity of marketable securities	1,127	0
Proceeds from the sale of property, plant and equipment and other assets	1	1
Net Cash Used in Investing Activities	(1,013)	(1,016)
Cash Flows from Financing Activities:
Long-term debt borrowings, net of issuance costs	4,569	764
Payments on and repurchases of long-term debt and capital leases	(4,917)	(818)
Net Cash Used in Financing Activities	(348)	(54)
Effect of Exchange Rates on Cash and Cash Equivalents	3	(1)
Net Change in Cash and Cash Equivalents	433	715
Cash and Cash Equivalents at Beginning of Period	1,819	854
Cash and Cash Equivalents at End of Period	2,252	1,569
Supplemental Disclosure of Cash Flow Information:
Cash interest paid	412	372
Income taxes paid, net of refunds	$ 47	$ 26