Commitments and Contingencies Off-Balance Sheet Commitments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Obligation with Joint and Several Liability Arrangement, Amount Outstanding	$ 1,174,670	$ 1,025,895
Standby Letters Of Credit, Final Expiration	2035
Other Liabilities	$ 366	362
Commitments to purchase mortgage loans, maximum term	60 days
Total consolidated obligations, par value	$ 117,062	98,817
Assets Pledged As Collateral	1,725	759
Security Owned and Pledged as Collateral, Fair Value	643	381
Derivative, Collateral, Right to Reclaim Cash	1,082	378
Standby letters of credit outstanding
Loss Contingencies [Line Items]
Expire Within One Year	15,207	16,898
Expire After One Year	4,954	4,658
Total	20,161	21,556
Other Liabilities	33	32
Loan Origination Commitments [Member]
Loss Contingencies [Line Items]
Expire Within One Year	24	0
Expire After One Year	0	0
Total	24	0
Commitments to issue consolidated obligation discount notes, par
Loss Contingencies [Line Items]
Expire Within One Year	250	805
Expire After One Year	0	0
Total	250	805
Commitments to issue consolidated obligation bonds, par
Loss Contingencies [Line Items]
Expire Within One Year	1,160	0
Expire After One Year	0	0
Total	$ 1,160	0
Minimum | Standby letters of credit outstanding
Loss Contingencies [Line Items]
Guarantor Obligations, Term	2 days
Maximum | Standby letters of credit outstanding
Loss Contingencies [Line Items]
Guarantor Obligations, Term	15 years
Guarantee of Indebtedness of Others
Loss Contingencies [Line Items]
Total consolidated obligations, par value	$ 117,062	98,817
Mortgages | Commitments to purchase mortgage loans
Loss Contingencies [Line Items]
Expire Within One Year	87	46
Expire After One Year	0	0
Total	$ 87	$ 46