Preparation Of Interim Financial Statements (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Change in Accounting Principle [Line Items]
Other cost of services	$ 9,214	$ 8,866	$ 27,604	$ 26,167
Income tax expense	1,657	1,444	4,784	5,914
Net income	3,078	3,187	9,601	10,654
Net Income attributable to AT&T	$ 2,994	$ 3,130	$ 9,339	$ 10,441
Basic Earnings Per Share Attributable to AT&T	$ 0.50	$ 0.60	$ 1.71	$ 2.00
Diluted Earnings Per Share Attributable to AT&T	$ 0.50	$ 0.60	$ 1.71	$ 2.00
Other current assets	$ 11,254		$ 11,254		$ 9,802
Other Assets	13,585		13,585		13,659
Accrued taxes	4,591		4,591		1,136
Deferred income taxes	53,044		53,044		38,549
Retained Earnings	32,627		32,627		31,081
Historical Accounting Method [Member]
Change in Accounting Principle [Line Items]
Other cost of services	9,290	$ 9,071	27,842	$ 26,552
Income tax expense	1,628	1,367	4,694	5,769
Net income	3,031	3,059	9,453	10,414
Net Income attributable to AT&T	$ 2,947	$ 3,002	$ 9,191	$ 10,201
Basic Earnings Per Share Attributable to AT&T	$ 0.50	$ 0.58	$ 1.68	$ 1.96
Diluted Earnings Per Share Attributable to AT&T	$ 0.50	$ 0.58	$ 1.68	$ 1.95
Other current assets	$ 9,579		$ 9,579		8,067
Other Assets	10,671		10,671		10,998
Accrued taxes					1,091
Deferred income taxes	51,949		51,949		37,544
Retained Earnings	29,133		29,133		27,736
Effect of Change [Member]
Change in Accounting Principle [Line Items]
Other cost of services	(76)	$ (205)	(238)	$ (385)
Income tax expense	29	77	90	145
Net income	47	128	148	240
Net Income attributable to AT&T	$ 47	$ 128	$ 148	$ 240
Basic Earnings Per Share Attributable to AT&T	$ 0	$ 0.02	$ 0.03	$ 0.04
Diluted Earnings Per Share Attributable to AT&T	$ 0	$ 0.02	$ 0.03	$ 0.05
Other current assets	$ 1,675		$ 1,675		1,735
Other Assets	2,914		2,914		2,661
Accrued taxes					45
Deferred income taxes	1,095		1,095		1,005
Retained Earnings	$ 3,494		$ 3,494		$ 3,345