Investment Securities - Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Securities Available for Sale and Held to Maturity (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2025	Dec. 31, 2024
Available for sale securities
Amortized Cost	$ 72,604	$ 89,704
Gross Unrealized Gains	2	1
Gross Unrealized Losses	4,994	6,711
Fair Value	67,612	82,994
Unallocated portfolio layer method fair value basis adjustments, Amortized Cost	9	(47)
Unallocated portfolio layer method fair value basis adjustments, Gross Unrealized Gains	0	0
Unallocated portfolio layer method fair value basis adjustments, Gross Unrealized Losses	9	(47)
Held to maturity securities
Amortized Cost	139,684	146,453
Gross Unrealized Gains	1,442	146
Gross Unrealized Losses	11,125	13,994
Fair Value	130,001	132,605
U.S. agency mortgage-backed securities
Available for sale securities
Amortized Cost	50,282	57,262
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,992	5,429
Fair Value	46,290	51,833
Held to maturity securities
Amortized Cost	139,684	146,453
Gross Unrealized Gains	1,442	146
Gross Unrealized Losses	11,125	13,994
Fair Value	130,001	132,605
U.S. Treasury securities
Available for sale securities
Amortized Cost	9,674	14,939
Gross Unrealized Gains	1	1
Gross Unrealized Losses	284	471
Fair Value	9,391	14,469
Corporate debt securities
Available for sale securities
Amortized Cost	6,717	10,166
Gross Unrealized Gains	0	0
Gross Unrealized Losses	476	587
Fair Value	6,241	9,579
Asset-backed securities
Available for sale securities
Amortized Cost	4,852	6,106
Gross Unrealized Gains	1	0
Gross Unrealized Losses	179	196
Fair Value	4,674	5,910
U.S. state and municipal securities
Available for sale securities
Amortized Cost	599	603
Gross Unrealized Gains	0	0
Gross Unrealized Losses	42	54
Fair Value	557	549
Foreign government agency securities
Available for sale securities
Amortized Cost	329	533
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	6
Fair Value	329	527
Non-agency commercial mortgage-backed securities
Available for sale securities
Amortized Cost	121	121
Gross Unrealized Gains	0	0
Gross Unrealized Losses	10	12
Fair Value	111	109
Other
Available for sale securities
Amortized Cost	21	21
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2	3
Fair Value	$ 19	$ 18
Corporate Debt Securities Issued By Financial Services Industry
Held to maturity securities
AFS securities percentage	26.00%	35.00%
Corporate Debt Securities Issued By Technology Industry
Held to maturity securities
AFS securities percentage	21.00%	16.00%
Corporate Debt Securities Issued By Consumer Staples Industry
Held to maturity securities
AFS securities percentage	20.00%	18.00%
Federal Family Education Loan Program (FFELP) Guaranteed Loans \| Asset-backed securities \| Financial Instrument Concentration Risk
Held to maturity securities
Concentration risk percentage	74.00%	62.00%
Collateralized Credit Card Securities \| Asset-backed securities \| Financial Instrument Concentration Risk
Held to maturity securities
Concentration risk percentage	19.00%	25.00%

Concentration Risk, Available-For-Sale

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Hedged Asset, Fair Value Hedge, Portfolio Layer Method, Hedged Layer, Accumulated Gross Unrealized Gain, Before Tax, Cumulative Increase (Decrease)

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Hedged Asset, Fair Value Hedge, Portfolio Layer Method, Hedged Layer, Accumulated Gross Unrealized Loss, Before Tax, Cumulative Increase (Decrease)

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amortized cost excluding accrued interest, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount excluding accrued interest, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, in portfolio layer hedging relationship.

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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