Allowance for Loan Losses and Total Recorded Investment in HFI Loans (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses for individually impaired loans	$ 18,124		$ 21,953
Allowance for loan losses for collectively reserved loans	2,070		1,512
Total allowance for loan losses	20,194	$ 20,399	23,465	$ 22,706	$ 23,799	$ 27,951
Recorded investment in individually impaired loans	140,592		156,187
Recorded investment in collectively reserved loans	3,024,739		2,939,629
Total recorded investment in loans	3,165,331		3,095,816
Single-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses for individually impaired loans	18,089		21,920
Allowance for loan losses for collectively reserved loans	1,883		1,363
Total allowance for loan losses	19,972	20,218	23,283	22,516	23,584	27,709
Recorded investment in individually impaired loans	140,007		155,598
Recorded investment in collectively reserved loans	2,770,331		2,708,337
Total recorded investment in loans	2,910,338		2,863,935
Multifamily [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses for individually impaired loans	35		33
Allowance for loan losses for collectively reserved loans	187		149
Total allowance for loan losses	222	$ 181	182	$ 190	$ 215	$ 242
Recorded investment in individually impaired loans	585		589
Recorded investment in collectively reserved loans	254,408		231,292
Total recorded investment in loans	$ 254,993		$ 231,881