Fair Value of Financial Instruments - Summary of Estimated Fair Values of Financial Instruments not Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturities, fair value	$ 97,227	$ 17,217
Net loans	65,854	44,733
Time deposits	1,739	688
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	14,619	17,675
Held-to-maturities, fair value	98,195	16,592
Non-marketable securities not measured at net asset value	424	241
Non-marketable securities measured at net asset value	710	390
Net loans	65,854	44,734
FHLB and FRB stock	107	61
Non-maturity deposits	187,464	101,294
Time deposits	1,739	688
Junior subordinated debentures	90
Commitments to extend credit	0	0
Carrying Amount | Other short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	121	21
Carrying Amount | 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	349	349
Carrying Amount | 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	496	495
Carrying Amount | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	494
Carrying Amount | 2.100% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	496
Carrying Amount | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	645
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	14,619	17,675
Held-to-maturities, fair value	97,227	17,217
Non-marketable securities not measured at net asset value	424	241
Non-marketable securities measured at net asset value	710	390
Net loans	67,335	45,324
FHLB and FRB stock	107	61
Non-maturity deposits	187,464	101,294
Time deposits	1,728	502
Junior subordinated debentures	92
Commitments to extend credit	47	37
Estimated Fair Value | Other short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	121	21
Estimated Fair Value | 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	370	383
Estimated Fair Value | 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	526	564
Estimated Fair Value | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	474
Estimated Fair Value | 2.100% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	501
Estimated Fair Value | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	649
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	14,619	17,675
Held-to-maturities, fair value	0	0
Non-marketable securities not measured at net asset value	0	0
Net loans	0	0
FHLB and FRB stock	0	0
Non-maturity deposits	187,464	101,294
Time deposits	0	0
Junior subordinated debentures	0
Commitments to extend credit	0	0
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	0	0
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0	0
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0	0
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | 2.100% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0
Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Held-to-maturities, fair value	97,227	17,217
Non-marketable securities not measured at net asset value	0	0
Net loans	0	0
FHLB and FRB stock	0	0
Non-maturity deposits	0	0
Time deposits	1,728	502
Junior subordinated debentures	92
Commitments to extend credit	0	0
Estimated Fair Value | Significant Other Observable Inputs (Level 2) | Other short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	121	21
Estimated Fair Value | Significant Other Observable Inputs (Level 2) | 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	370	383
Estimated Fair Value | Significant Other Observable Inputs (Level 2) | 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	526	564
Estimated Fair Value | Significant Other Observable Inputs (Level 2) | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	474
Estimated Fair Value | Significant Other Observable Inputs (Level 2) | 2.100% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	501
Estimated Fair Value | Significant Other Observable Inputs (Level 2) | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	649
Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Held-to-maturities, fair value	0	0
Non-marketable securities not measured at net asset value	424	241
Net loans	67,335	45,324
FHLB and FRB stock	107	61
Non-maturity deposits	0	0
Time deposits	0	0
Junior subordinated debentures	0
Commitments to extend credit	47	37
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | Other short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	0	0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0	0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0	$ 0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | 2.100% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	$ 0