Acquisition and Divestiture Activity (Narrative) (Details) - USD ($)		1 Months Ended	3 Months Ended	6 Months Ended
	Jun. 01, 2021	May 31, 2020	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill			$ 10,958,000,000	$ 10,958,000,000			$ 9,233,000,000
Gain on disposition of business					$ 5,740,000,000
Goodwill impairment charge				0	0
ACL at acquisition			1,115,000,000	1,115,000,000
Total allowance			5,730,000,000	$ 5,730,000,000	5,928,000,000	$ 4,714,000,000	$ 5,361,000,000	$ 3,944,000,000	$ 2,742,000,000
BBVA USA Bancshares, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment charge					$ 2,200,000,000
Core deposits
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Useful life				10 years
Non-PCD Loans
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total allowance			1,000,000,000.0	$ 1,000,000,000.0
Discontinued Operations, Disposed of by Sale | BlackRock, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposition of business		$ 4,300,000,000
Discontinued operations, number of shares contributed		500,000
Registered Secondary Offering | Discontinued Operations, Disposed of by Sale | BlackRock, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposition of business		$ 4,300,000,000
Sale of stock, number of shares issued in transaction (in shares)		31,600,000
Sale of stock, price per share (in dollars per share)		$ 420
Sale of stock, consideration received on transaction		$ 14,200,000,000
Payments of stock issuance costs		$ 200,000,000
BlackRock, Inc. | Discontinued Operations, Disposed of by Sale | BlackRock, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		2,650,000
Sale of stock, price per share (in dollars per share)		$ 414.96
BBVA USA Bancshares, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business combination, consideration transferred	$ 11,480,000,000
Acquisition costs			$ 111,000,000	117,000,000
Cumulative nonrecurring merger and integration costs				$ 124,000,000
Goodwill	1,640,000,000
ACL at acquisition	1,161,000,000
Total loans and leases	61,370,000,000
BBVA USA Bancshares, Inc. | Fair Value
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loans and leases	61,370,000,000
BBVA USA Bancshares, Inc. | Carrying Amount
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loans and leases	62,269,000,000
BBVA USA Bancshares, Inc. | Non-PCD Loans | Fair Value
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loans and leases	52,100,000,000
BBVA USA Bancshares, Inc. | Non-PCD Loans | Carrying Amount
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loans and leases	52,000,000,000.0
BBVA USA Bancshares, Inc. | Purchased Impaired Loans | Fair Value
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loans and leases	9,300,000,000
BBVA USA Bancshares, Inc. | Purchased Impaired Loans | Carrying Amount
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total loans and leases	$ 10,300,000,000