Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Revenue	$ 2,061	$ 2,056	$ 4,109	$ 4,107
Costs and Expenses:
Network access costs	675	676	1,366	1,370
Network related expenses	337	339	673	677
Depreciation and amortization	330	310	650	611
Selling, general and administrative Expenses	366	357	730	713
Total Costs and Expenses	1,708	1,682	3,419	3,371
Operating Income	353	374	690	736
Other Income (Expense):
Interest income	3	1	5	2
Interest expense	(132)	(140)	(266)	(275)
Loss on modification and extinguishment of Debt	0	(40)	(44)	(40)
Other, net	(1)	(5)	3	(15)
Total Other Expense	(130)	(184)	(302)	(328)
Income Before Income Taxes	223	190	388	408
Income Tax Expense	(69)	(34)	(139)	(124)
Net Income	$ 154	$ 156	$ 249	$ 284
Basic Earnings per Common Share
Net Income Per Share	$ 0.42	$ 0.44	$ 0.69	$ 0.79
Weighted-Average Shares Outstanding (in thousands)	362,385	357,924	361,942	357,355
Diluted Earnings per Common Share
Net Income Per Share	$ 0.42	$ 0.43	$ 0.68	$ 0.79
Weighted-Average Shares Outstanding (in thousands)	365,002	361,250	364,569	360,804