Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2023	Dec. 31, 2022
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	$ 8,723
Debt securities, available-for-sale	8,723	$ 9,060
Equity securities:
Equity securities, Fair Value	13	14
Interest receivable	39	31
Marketable securities amortized cost	9,917	9,933
Marketable securities gross unrealized gain	9	14
Marketable securities gross unrealized loss	1,190	873
Total securities	8,736	9,074
Agency - commercial
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	6,438	5,242
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	7
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	749	460
Debt securities, available-for-sale	5,689	4,789
Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	3,463	4,675
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	9	7
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	438	411
Debt securities, available-for-sale	3,034	4,271
Mortgage Backed Securities And Other Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	9,901	9,917
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	9	14
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1,187	871
Debt securities, available-for-sale	8,723	9,060
Equity Securities
Equity securities:
Equity securities, Fair Value	13	14
Equity securities, Amortized Cost	16	16
Equity securities, Gross Unrealized Loss	3	2
GSE certificates \| Agency - commercial
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	1,378	1,457
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	214	160
Debt securities, available-for-sale	1,164	1,297
GSE CMOs \| Agency - commercial
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	4,883	3,600
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	1
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	532	300
Debt securities, available-for-sale	4,351	3,301
Private Label CMOs
Debt securities available-for-sale
Debt securities, available-for-sale	174
Private Label CMOs \| Agency - commercial
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	177	185
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	6
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	3	0
Debt securities, available-for-sale	174	191
U. S. Treasury obligations \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	195	1,491
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	0	4
Debt securities, available-for-sale	195	1,487
GSE debentures \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	2,041	1,749
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	1	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	383	351
Debt securities, available-for-sale	1,659	1,398
Asset-backed securities \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	319	375
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	6	14
Debt securities, available-for-sale	313	361
Municipal bonds \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	7	30
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	1	0
Debt securities, available-for-sale	6	30
Corporate bonds \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	769	913
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	3	2
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	35	30
Debt securities, available-for-sale	737	885
Foreign notes \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	35	20
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0	0
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	2	0
Debt securities, available-for-sale	33	20
Capital trust notes \| Debt Securities
Debt securities available-for-sale
Debt securities, available-for-sale, amortized cost, total	97	97
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	5	5
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	11	12
Debt securities, available-for-sale	91	90
Mutual funds and common stock \| Equity Securities
Equity securities:
Equity securities, Fair Value	13	14
Equity securities, Amortized Cost	16	16
Equity securities, Gross Unrealized Loss	$ 3	$ 2

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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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