Additional Financial Information (Preferred Interest) (Details) $ / shares in Units, $ in Millions	1 Months Ended	4 Months Ended	9 Months Ended
	Jun. 30, 2023 USD ($) $ / shares shares	Apr. 30, 2023 USD ($) shares	Sep. 30, 2023 period shares	Dec. 31, 2022 shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Option to require redemption, certain contingent events, failure of Telco LLC to pay preferred distributions, minimum number of periods | period			2
Preferred Stock - Series A
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Preferred stock, issued (in shares) | shares			48,000	48,000
Preferred Stock - Series B
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Preferred stock, issued (in shares) | shares			20,000	20,000
Telco LLC
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Nonconvertible cumulative preferred interests issued		$ 7,250
Telco LLC | Class A-2 And Class A-3
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Nonconvertible cumulative preferred interests issued		$ 5,250
Initial preferred distribution percentage		6.85%
Distribution reset period		7 years
AT&T Mobility II, LLC | Preferred Stock - Series A
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock Redeemed or Called During Period, Shares | shares		213,000,000
Stock Redeemed or Called During Period, Value		$ 5,414
Put or redemption option, minimum exercise price calculation, value added to accrued and unpaid distributions in the aggregate		5,320
AT&T Mobility II, LLC | Preferred Stock - Series B
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Initial preferred distribution percentage	6.80%
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 2,000
Preferred stock, issued (in shares) | shares	2,000,000
Put or redemption option, minimum exercise price calculation, value added to accrued and unpaid distributions (in dollars per share) | $ / shares	$ 1,000
AT&T Mobility II, LLC | Accounts payable and accrued liabilities | Preferred Stock - Series A
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Put or redemption option, minimum exercise price calculation, value added to accrued and unpaid distributions in the aggregate		2,650
AT&T Mobility II, LLC | Other Noncurrent Liabilities | Preferred Stock - Series A
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Put or redemption option, minimum exercise price calculation, value added to accrued and unpaid distributions in the aggregate		$ 2,670