Allowance for Credit Losses on Loans and Leases - Schedule of Activity in the Allowance for Loan and Lease Losses (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 1,215	$ 550	$ 992	$ 393	$ 393
Adjustment for Purchased PCD Loans				13
Charge-offs	(354)	(3)	(445)	(8)
Recoveries	5	4	14	9
Provision for (recovery of) credit losses on loans and leases	402	43	707	187
Balance, end of period	1,268	594	1,268	594	992
Loans and Leases Held for Investment: \| Multi-family
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	469	171	307	178	178
Adjustment for Purchased PCD Loans				0
Charge-offs	(76)	0	(87)	0	(119)
Recoveries	0	0	1	0
Provision for (recovery of) credit losses on loans and leases	225	21	397	14
Balance, end of period	618	192	618	192	307
Loans and Leases Held for Investment: \| Commercial real estate
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	434	53	366	46	46
Adjustment for Purchased PCD Loans				0
Charge-offs	(237)	0	(301)	0	(56)
Recoveries	0	0	0	0
Provision for (recovery of) credit losses on loans and leases	131	16	263	23
Balance, end of period	328	69	328	69	366
Loans and Leases Held for Investment: \| One-to-four family first mortgage
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	42	39	47	46	46
Adjustment for Purchased PCD Loans				0
Charge-offs	(1)	(1)	(1)	(2)	(3)
Recoveries	0	0	0	0
Provision for (recovery of) credit losses on loans and leases	(1)	7	(6)	1
Balance, end of period	40	45	40	45	47
Loans and Leases Held for Investment: \| Acquisition, development, and construction
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	48	20	36	20	20
Adjustment for Purchased PCD Loans				0
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0
Provision for (recovery of) credit losses on loans and leases	(5)	3	7	3
Balance, end of period	43	23	43	23	36
Other
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	222	267	236	103	103
Adjustment for Purchased PCD Loans				13
Charge-offs	(40)	(2)	(56)	(6)
Recoveries	5	4	13	9
Provision for (recovery of) credit losses on loans and leases	52	(4)	46	146
Balance, end of period	$ 239	$ 265	$ 239	$ 265	$ 236

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

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Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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Amount, excluding accrued interest, of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-19

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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