Commitments, Guarantees, Contingent Liabilities, and Related Parties (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Guarantor Obligations [Line Items]
Commitments to extend credit expiring in one year	$ 7,700
Standby letters of credit expiring in one year	398
Standby letters of credit, thereafter	300
Letters of credit, accrued liability	6
Reserve for unfunded lending commitments	4
Deferred commitment fees	2
Risk-weighted values assigned to all off-balance sheet financial and derivative instruments	8,500	$ 8,300
Minimum
Guarantor Obligations [Line Items]
Estimate of possible losses	0
Maximum
Guarantor Obligations [Line Items]
Estimate of possible losses	$ 35