Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities:
Net Income	$ 249	$ 284
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	650	611
Non-cash compensation expense attributable to stock awards	87	78
Loss on modification and extinguishment of debt	44	40
Accretion of debt discount and amortization of debt issuance costs	9	10
Accrued interest on long-term debt, net	(32)	23
Deferred income taxes	119	101
Gain on sale of property, plant and equipment and other assets	0	(1)
Other, net	(8)	(3)
Changes in working capital items:
Receivables	16	(69)
Other current assets	(36)	(40)
Accounts payable	(17)	132
Deferred revenue	50	42
Other current liabilities	(31)	(67)
Net Cash Provided by Operating Activities	1,100	1,141
Cash Flows from Investing Activities:
Capital expenditures	(696)	(664)
Change in restricted cash and securities, net	4	11
Purchases of marketable securities	(1,127)	0
Proceeds from the sale of property, plant and equipment and other assets	0	1
Net Cash Used in Investing Activities	(1,819)	(652)
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	(4,615)	(816)
Net Cash (Used in) Provided by Financing Activities	(46)	(52)
Effect of Exchange Rates on Cash and Cash Equivalents	2	0
Net Change in Cash and Cash Equivalents	(763)	437
Cash and Cash Equivalents at Beginning of Period	1,819	854
Cash and Cash Equivalents at End of Period	1,056	1,291
Supplemental Disclosure of Cash Flow Information:
Cash interest paid	282	245
Income taxes paid, net of refunds	$ 32	$ 18