Additional Financial Information (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Additional Financial Information [Line Items]
Payment of vendor financing		$ 2,601	$ 347
Tower Holdings [Member]
Additional Financial Information [Line Items]
Preferred interest issued by subsidiary, amount	$ 1,500
Preferred Interest, Description	The membership interests in Tower Holdings consist of (1) common interests, which are held by a consolidated subsidiary of AT&T, and (2) these newly issued preferred interests (Tower preferred interests), which pay an initial preferred distribution of 5.0% annually, subject to declaration, resetting every five years. The declaration and payment of distributions on the preferred interests do not impose any limitation on cash movements between affiliates, or our ability to declare a dividend on or repurchase AT&T shares. We can call the Tower preferred interests beginning five years from the issuance date or upon the receipt of proceeds from the sale of the underlying assets. The preferred interests are included in “Noncontrolling interest” on the consolidated balance sheet. The holders of the Tower preferred interests have the option to require redemption upon the occurrence of certain contingent events, such as the failure of AT&T to pay the preferred distribution for two or more periods or to meet certain other requirements, including a minimum credit rating. If notice is given upon such an event, all other holders of equal or more subordinate classes of membership interests in Tower Holdings are entitled to receive the same form of consideration payable to the holders of the preferred interests, resulting in a deemed liquidation for accounting purposes.
Vendor Financing Program [Member]
Additional Financial Information [Line Items]
Noncash Investing Activities		1,920
Payment of vendor financing		$ 2,601