Mortgage Loans Held for Portfolio (Payment Status) (Details) - Conventional Mortgage Loans [Member] - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	$ 10,888	$ 9,139
Financing Receivable, Past Due	14,185	11,531
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	3,297	2,392
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	61	41
Financing Receivable, Past Due	97	69
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	36	28
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	12	11
Financing Receivable, Past Due	20	19
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	8	8
Financing Receivables, 90 to 179 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	12	7
Financing Receivable, Past Due	18	12
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	6	5
Financing Receivables, Greater than 180 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	7	4
Financing Receivable, Past Due	11	8
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	4	4
Financial Asset, Not Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	10,796	9,076
Financing Receivable, Past Due	14,039	11,423
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	3,243	2,347
Financial Asset, Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated, Current Fiscal Year and Preceeding Four Preceeding Fiscal Years	92	63
Financing Receivable, Past Due	146	108
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Writeoff	$ 54	$ 45