UPB of Unconsolidated Loans by Payment Status (Details) $ in Millions	Mar. 31, 2020 USD ($)
Guarantor Obligations [Line Items]
UPB of Unconsolidated loans current	$ 340,265
UPB of Unconsolidated loans 30 to 59 days past due	1,994
UPB of Unconsolidated loans 60 to 89 days past due	672
UPB of Unconsolidated loans equal to or greater than 90 days past due	1,115
Total UPB of Unconsolidated loans by payment status	344,046
Single Family
Guarantor Obligations [Line Items]
UPB of Unconsolidated loans current	35,362
UPB of Unconsolidated loans 30 to 59 days past due	1,985
UPB of Unconsolidated loans 60 to 89 days past due	660
UPB of Unconsolidated loans equal to or greater than 90 days past due	861
Total UPB of Unconsolidated loans by payment status	38,868
Multifamily
Guarantor Obligations [Line Items]
UPB of Unconsolidated loans current	304,903
UPB of Unconsolidated loans 30 to 59 days past due	9
UPB of Unconsolidated loans 60 to 89 days past due	12
UPB of Unconsolidated loans equal to or greater than 90 days past due	254
Total UPB of Unconsolidated loans by payment status	$ 305,178