Mortgage Loans -Amortized Cost Basis of Multifamily Held- for-Investment Loans by Credit Quality Indicator by Vintage (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 3,291,359	$ 3,177,386
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	63,205	27,763
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	28,825	14,576
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	13,813	17,231
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	16,490	7,547
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	11	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	7,567	6,487
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	13,842	8,524
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	115	0
Revolving Loans	1,851	2,426
Financing Receivable, Excluding Accrued Interest, Revolving, Writeoff	0	0
Total	145,593	84,554
Full-year gross charge-offs	126	0
Pass | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	63,205	27,713
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	28,613	14,471
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	13,374	16,548
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	15,732	7,179
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	7,238	6,201
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	12,947	7,921
Revolving Loans	1,851	2,426
Total	142,960	82,459
Special mention | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	50
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	49	76
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	173	239
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	177	39
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	96	86
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	670	327
Revolving Loans	0	0
Total	1,165	817
Substandard | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	163	29
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	266	444
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	581	329
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	233	200
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	225	276
Revolving Loans	0	0
Total	1,468	1,278
Doubtful | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Revolving Loans	0	0
Total	$ 0	$ 0