Leases - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
|
| Lessee, Lease, Description [Line Items] | ||||
| Interest payments for financing leases | $ 20 | $ 21 | $ 40 | $ 41 |
| Additional operating leases not yet commenced, payments due | $ 340 | $ 340 | ||
| Device upgrade period | 18 months | |||
| Minimum | ||||
| Lessee, Lease, Description [Line Items] | ||||
| Lessee leasing arrangements, operating leases, term of contract (years) | 5 years | 5 years | ||
| Option to extend lease term | 5 years | |||
| Lessee leasing arrangements, finance leases, term of contract | 2 years | 2 years | ||
| Maximum | ||||
| Lessee, Lease, Description [Line Items] | ||||
| Lessee leasing arrangements, operating leases, term of contract (years) | 10 years | 10 years | ||
| Option to extend lease term | 35 years | |||
| Lessee leasing arrangements, finance leases, term of contract | 5 years | 5 years | ||