Allowance for Credit Losses on Loans and Leases - Schedule of Activity in the Allowance for Loan and Lease Losses (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	$ 992	$ 393	$ 199
Charge-offs	(938)	(223)	(7)
Recoveries	46	15	11
Provision for (recovery of) credit losses on loans and leases	1,101	794	139
Adjustment for Purchased PCD Loans		13	51
Balance, end of period	1,201	992	393
Loans held for investment \| Multi-family
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	307	178	159
Charge-offs	(308)	(119)	(1)
Recoveries	5	0	0
Provision for (recovery of) credit losses on loans and leases	635	248	11
Adjustment for Purchased PCD Loans		0	9
Balance, end of period	639	307	178
Loans held for investment \| Commercial real estate
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	366	47	17
Charge-offs	(462)	(56)	(4)
Recoveries	8	0	4
Provision for (recovery of) credit losses on loans and leases	348	375	12
Adjustment for Purchased PCD Loans		0	18
Balance, end of period	260	366	47
Loans held for investment \| One-to-four family first mortgage
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	47	46	0
Charge-offs	(8)	(4)	0
Recoveries	5	0	0
Provision for (recovery of) credit losses on loans and leases	(5)	5	29
Adjustment for Purchased PCD Loans		0	17
Balance, end of period	39	47	46
Loans held for investment \| Acquisition, development, and construction
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	36	20	3
Charge-offs	(4)	0	0
Recoveries	0	0	0
Provision for (recovery of) credit losses on loans and leases	12	16	10
Adjustment for Purchased PCD Loans		0	7
Balance, end of period	44	36	20
Other loans held for investment
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	236	102	20
Charge-offs	(156)	(44)	(2)
Recoveries	28	15	7
Provision for (recovery of) credit losses on loans and leases	111	150	77
Adjustment for Purchased PCD Loans		13	0
Balance, end of period	$ 219	$ 236	$ 102

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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph c
-Publisher SEC

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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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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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
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-Publisher FASB
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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

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