Commitments (Narrative) (Details) - USD ($) $ in Billions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Standby letters of credit | ||
| Loss Contingencies [Line Items] | ||
| Internal credit ratings (as a percentage of portfolio) - Pass | 91.00% | 91.00% |
| Internal credit ratings (as a percentage of portfolio) - Criticized | 9.00% | 9.00% |
| Standby letters of credit - Assets securing certain specifically identified standby letters of credit | $ 1.1 | |
| Standby letters of credit and participations in standby letters of credit - Liability carrying amount | $ 0.2 | |
| Less than 1 year | ||
| Loss Contingencies [Line Items] | ||
| Standby letters of credit, term | 1 year | |
| Maximum | ||
| Loss Contingencies [Line Items] | ||
| Standby letters of credit, term | 6 years |