Compensation Plans (401k Plans and Performance Fees) (Details) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2019
USD ($)
plan
|
Dec. 31, 2018
USD ($)
|
Dec. 31, 2017
USD ($)
|
|
| Share-based Payment Arrangement [Abstract] | |||
| Number of 401(k) plans (in plan) | plan | 2 | ||
| 401(k) savings plan employer contribution | $ | $ 724 | $ 691 | $ 448 |