Revenue and Contract Costs - Schedule of Receivables from Contracts with Customers (Details) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Revenue from Contract with Customer [Abstract] | ||
| Accounts Receivable | $ 9,593 | $ 9,646 |
| Device payment plan agreement receivables | $ 20,018 | $ 21,726 |