CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES
Net income	$ 163	$ 236
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	880	976
Deferred income taxes	(37)	11
Provision for uncollectible accounts	47	46
Net long-term debt issuance costs and premium amortization	1	(1)
Share-based compensation	21	18
Changes in current assets and liabilities:
Accounts receivable	116	26
Accounts payable	(81)	78
Accrued income and other taxes	206	160
Other current assets and liabilities, net	(266)	(72)
Retirement benefits	(25)	(21)
Changes in other noncurrent assets and liabilities, net	12	(35)
Other, net	20	1
Net cash provided by operating activities	1,057	1,423
INVESTING ACTIVITIES
Payments for property, plant and equipment and capitalized software	(780)	(611)
Proceeds from sale of property	45	7
Other, net	3	(1)
Net cash used in investing activities	(732)	(605)
FINANCING ACTIVITIES
Net proceeds from issuance of long-term debt	0	227
Payments of long-term debt	(31)	(25)
Net proceeds (payments) on credit facility and revolving line of credit	5	(410)
Dividends paid	(296)	(290)
Proceeds from issuance of common stock	3	4
Shares withheld to satisfy tax withholdings	(14)	(12)
Net cash used in financing activities	(333)	(506)
Net (decrease) increase in cash and cash equivalents	(8)	312
Cash and cash equivalents at beginning of period	222	126
Cash and cash equivalents at end of period	214	438
Supplemental cash flow information:
Income taxes refunded (paid), net	5	(11)
Interest paid (net of capitalized interest of $20 and $12)	$ (255)	$ (262)