Consolidated Statement Of Changes In Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income Attributable to AT&T, net of tax [Member]	Noncontrolling Interest [Member]
Balance at beginning of period at Dec. 31, 2017	$ 142,007	$ 6,495	$ 89,563	$ 50,500	$ (12,714)	$ 7,017	$ 1,146
Balance at beginning of period (in shares) at Dec. 31, 2017		6,495			(356)
Issuance of stock		$ 1,126	35,473
Issuance of stock (in shares)		1,126
Repurchase and acquisition of common stock					$ (641)
Repurchase and acquisition of common stock (in shares)					(19)
Issuance of treasury stock			(49)		$ 869
Issuance of treasury stock, (in shares)					24
Share-based payments			719
Net income attributable to AT&T ($0.50, $0.65, $1.57 and $2.19 per diluted share)	14,512			14,512
Dividends to stockholders ($0.51, $0.50, $1.53 and $1.50 per share)				(10,388)
Other comprehensive income attributable to AT&T						(976)
Net income attributable to noncontrolling interest	311						311
Interest acquired by noncontrolling owners							8
Distributions							(332)
Acquisitions of noncontrolling interest							1
Change related to acquisition of interests held by noncontrolling owners							(9)
Balance at end of period at Sep. 30, 2018	184,971	$ 7,621	125,706	57,624	$ (12,486)	5,383	1,123
Translation adjustments attributable to noncontrolling interest, net of taxes	(37)						(37)
Balance at end of period (in shares) at Sep. 30, 2018		7,621			(351)
Balance at beginning of period at Jun. 30, 2018	184,130	$ 7,621	125,960	56,555	$ (12,872)	5,716	1,150
Balance at beginning of period (in shares) at Jun. 30, 2018		7,621			(361)
Issuance of stock		$ 0	0
Issuance of stock (in shares)		0
Repurchase and acquisition of common stock					$ (34)
Repurchase and acquisition of common stock (in shares)					(1)
Issuance of treasury stock			(45)		$ 420
Issuance of treasury stock, (in shares)					11
Share-based payments			(209)
Net income attributable to AT&T ($0.50, $0.65, $1.57 and $2.19 per diluted share)	4,718			4,718
Dividends to stockholders ($0.51, $0.50, $1.53 and $1.50 per share)				(3,649)
Other comprehensive income attributable to AT&T						(333)
Net income attributable to noncontrolling interest	98						98
Interest acquired by noncontrolling owners							0
Distributions							(109)
Acquisitions of noncontrolling interest							0
Change related to acquisition of interests held by noncontrolling owners							(9)
Balance at end of period at Sep. 30, 2018	184,971	$ 7,621	125,706	57,624	$ (12,486)	5,383	1,123
Translation adjustments attributable to noncontrolling interest, net of taxes	(7)						(7)
Balance at end of period (in shares) at Sep. 30, 2018		7,621			(351)
Balance at beginning of period at Dec. 31, 2018	193,884	$ 7,621	125,525	58,753	$ (12,059)	4,249	9,795
Balance at beginning of period (in shares) at Dec. 31, 2018		7,621			(339)
Issuance of stock		$ 0	0
Issuance of stock (in shares)		0
Repurchase and acquisition of common stock					$ (466)
Repurchase and acquisition of common stock (in shares)					(14)
Issuance of treasury stock			(128)		$ 1,330
Issuance of treasury stock, (in shares)					36
Share-based payments			(258)
Net income attributable to AT&T ($0.50, $0.65, $1.57 and $2.19 per diluted share)	11,509			11,509
Dividends to stockholders ($0.51, $0.50, $1.53 and $1.50 per share)				(11,231)
Other comprehensive income attributable to AT&T						(2,112)
Net income attributable to noncontrolling interest	762						762
Interest acquired by noncontrolling owners							1,498
Distributions							(791)
Acquisitions of noncontrolling interest							0
Change related to acquisition of interests held by noncontrolling owners							0
Balance at end of period at Sep. 30, 2019	194,327	$ 7,621	125,139	59,347	$ (11,195)	2,137	11,278
Translation adjustments attributable to noncontrolling interest, net of taxes	(15)						(15)
Balance at end of period (in shares) at Sep. 30, 2019		7,621			(317)
Balance at beginning of period at Jun. 30, 2019	194,081	$ 7,621	125,109	59,389	$ (11,151)	3,289	9,824
Balance at beginning of period (in shares) at Jun. 30, 2019		7,621			(316)
Issuance of stock		$ 0	0
Issuance of stock (in shares)		0
Repurchase and acquisition of common stock					$ (186)
Repurchase and acquisition of common stock (in shares)					(5)
Issuance of treasury stock			(1)		$ 142
Issuance of treasury stock, (in shares)					4
Share-based payments			31
Net income attributable to AT&T ($0.50, $0.65, $1.57 and $2.19 per diluted share)	3,700			3,700
Dividends to stockholders ($0.51, $0.50, $1.53 and $1.50 per share)				(3,742)
Other comprehensive income attributable to AT&T						(1,152)
Net income attributable to noncontrolling interest	249						249
Interest acquired by noncontrolling owners							1,488
Distributions							(266)
Acquisitions of noncontrolling interest							0
Change related to acquisition of interests held by noncontrolling owners							0
Balance at end of period at Sep. 30, 2019	194,327	$ 7,621	$ 125,139	$ 59,347	$ (11,195)	$ 2,137	11,278
Translation adjustments attributable to noncontrolling interest, net of taxes	$ (17)						$ (17)
Balance at end of period (in shares) at Sep. 30, 2019		7,621			(317)