Investment Securities - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Investment securities available for sale
Investment securities available for sale, cost	$ 9,726	$ 9,215
Investment securities available for sale, gross unrealized gains	11	45
Investment securities available for sale, gross unrealized losses	(442)	(57)
Investment securities available for sale	9,295	9,203
Investment in marketable equity securities
Investment in marketable equity securities at cost	73	73
Investment in marketable equity, gross unrealized gains	27	25
Investment in marketable equity, gross unrealized losses	0	0
Investment in marketable equity, fair value	100	98
Investment securities held to maturity
Investment securities held to maturity, cost	10,074	3,809
Investment securities held to maturity, gross unrealized gains	0	6
Investment securities held to maturity, gross unrealized losses	(617)	(56)
Investment securities held to maturity, cost, fair value	9,457	3,759
Total investment securities
Total investment securities, amortized cost	19,873	13,097
Total investment securities, gross unrealized gains	38	76
Total investment securities, gross unrealized losses	(1,059)	(113)
Total investment securities, fair value	18,852	13,060
U.S. Treasury
Investment securities available for sale
Investment securities available for sale, cost	2,014	2,007
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	(83)	(2)
Investment securities available for sale	1,931	2,005
Investment securities held to maturity
Investment securities held to maturity, cost	471
Investment securities held to maturity, gross unrealized gains	0
Investment securities held to maturity, gross unrealized losses	(24)
Investment securities held to maturity, cost, fair value	447
Government agency
Investment securities available for sale
Investment securities available for sale, cost	206	221
Investment securities available for sale, gross unrealized gains	1	1
Investment securities available for sale, gross unrealized losses	(1)	(1)
Investment securities available for sale	206	221
Investment securities held to maturity
Investment securities held to maturity, cost	1,541
Investment securities held to maturity, gross unrealized gains	0
Investment securities held to maturity, gross unrealized losses	(78)
Investment securities held to maturity, cost, fair value	1,463
Residential mortgage-backed securities
Investment securities available for sale
Investment securities available for sale, cost	5,340	4,757
Investment securities available for sale, gross unrealized gains	0	8
Investment securities available for sale, gross unrealized losses	(288)	(36)
Investment securities available for sale	5,052	4,729
Investment securities held to maturity
Investment securities held to maturity, cost	4,776	2,322
Investment securities held to maturity, gross unrealized gains	0	6
Investment securities held to maturity, gross unrealized losses	(315)	(22)
Investment securities held to maturity, cost, fair value	4,461	2,306
Commercial mortgage-backed securities
Investment securities available for sale
Investment securities available for sale, cost	1,584	1,648
Investment securities available for sale, gross unrealized gains	2	9
Investment securities available for sale, gross unrealized losses	(66)	(17)
Investment securities available for sale	1,520	1,640
Investment securities held to maturity
Investment securities held to maturity, cost	2,988	1,485
Investment securities held to maturity, gross unrealized gains	0	0
Investment securities held to maturity, gross unrealized losses	(183)	(34)
Investment securities held to maturity, cost, fair value	2,805	1,451
Corporate bonds
Investment securities available for sale
Investment securities available for sale, cost	582	582
Investment securities available for sale, gross unrealized gains	8	27
Investment securities available for sale, gross unrealized losses	(4)	(1)
Investment securities available for sale	586	608
Supranational securities
Investment securities held to maturity
Investment securities held to maturity, cost	294
Investment securities held to maturity, gross unrealized gains	0
Investment securities held to maturity, gross unrealized losses	(17)
Investment securities held to maturity, cost, fair value	277
Other
Investment securities held to maturity
Investment securities held to maturity, cost	4	2
Investment securities held to maturity, gross unrealized gains	0	0
Investment securities held to maturity, gross unrealized losses	0	0
Investment securities held to maturity, cost, fair value	$ 4	2
State, county and municipal
Investment securities available for sale
Investment securities available for sale, cost		0
Investment securities available for sale, gross unrealized gains		0
Investment securities available for sale, gross unrealized losses		0
Investment securities available for sale		$ 0

Equity Securities FV-NI, Accumulated Gross Unrealized Gain, before Tax

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Equity Securities FV-NI, Accumulated Gross Unrealized Loss, before Tax

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Investments, Accumulated Unrecognized Gain

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Investments, Amortized Cost

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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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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 of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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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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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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