Leases - Narrative (Details) - USD ($) $ in Millions |
12 Months Ended | |||
|---|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Apr. 30, 2018 |
|
| Lessee, Lease, Description [Line Items] | ||||
| Variable lease cost | $ 380 | $ 327 | ||
| Lease liability, future minimum commitment | $ 1,618 | |||
| Operating leases, rent expense, net | $ 301 | |||
| Office Building In New York City [Member] | ||||
| Lessee, Lease, Description [Line Items] | ||||
| Operating lease term | 20 years | |||
| Lease liability, future minimum commitment | $ 1,600 | |||
| Minimum [Member] | ||||
| Lessee, Lease, Description [Line Items] | ||||
| Operating lease term | 1 year | |||
| Operating lease term, option to extend | 5 years | |||
| Maximum [Member] | ||||
| Lessee, Lease, Description [Line Items] | ||||
| Operating lease term | 30 years | |||
| Operating lease term, option to extend | 10 years | |||