Acquisition and Divestiture Activity (Fair Value and Unpaid Principal Balance of Loans Acquired) (Details) - BBVA USA Bancshares, Inc. $ in Millions	Jun. 01, 2021 USD ($)
Business Acquisition [Line Items]
Net loans	$ 61,423
Carrying Amount
Business Acquisition [Line Items]
Net loans	62,269
Fair Value
Business Acquisition [Line Items]
Net loans	61,423
Total commercial lending | Carrying Amount
Business Acquisition [Line Items]
Net loans	40,544
Total commercial lending | Fair Value
Business Acquisition [Line Items]
Net loans	39,742
Total commercial lending | Commercial and industrial | Carrying Amount
Business Acquisition [Line Items]
Net loans	29,864
Total commercial lending | Commercial and industrial | Fair Value
Business Acquisition [Line Items]
Net loans	29,381
Total commercial lending | Commercial real estate | Carrying Amount
Business Acquisition [Line Items]
Net loans	10,632
Total commercial lending | Commercial real estate | Fair Value
Business Acquisition [Line Items]
Net loans	10,313
Total commercial lending | Equipment lease financing | Carrying Amount
Business Acquisition [Line Items]
Net loans	48
Total commercial lending | Equipment lease financing | Fair Value
Business Acquisition [Line Items]
Net loans	48
Total consumer lending | Carrying Amount
Business Acquisition [Line Items]
Net loans	21,725
Total consumer lending | Fair Value
Business Acquisition [Line Items]
Net loans	21,681
Total consumer lending | Residential real estate | Carrying Amount
Business Acquisition [Line Items]
Net loans	12,871
Total consumer lending | Residential real estate | Fair Value
Business Acquisition [Line Items]
Net loans	12,961
Total consumer lending | Home equity | Carrying Amount
Business Acquisition [Line Items]
Net loans	2,430
Total consumer lending | Home equity | Fair Value
Business Acquisition [Line Items]
Net loans	2,423
Total consumer lending | Automobile | Carrying Amount
Business Acquisition [Line Items]
Net loans	3,916
Total consumer lending | Automobile | Fair Value
Business Acquisition [Line Items]
Net loans	3,910
Total consumer lending | Credit card | Carrying Amount
Business Acquisition [Line Items]
Net loans	820
Total consumer lending | Credit card | Fair Value
Business Acquisition [Line Items]
Net loans	758
Total consumer lending | Other consumer | Carrying Amount
Business Acquisition [Line Items]
Net loans	1,688
Total consumer lending | Other consumer | Fair Value
Business Acquisition [Line Items]
Net loans	$ 1,629