Capital (Regulatory Capital Requirements) (Details) $ in Millions	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Capital [Abstract]
Number of Finance Agency Regulatory Capital Requirements	3
Multiplier for Determining Permanent Capital in Leverage Capital Calculation	1.5
Multiplier for Determining Nonpermanent Capital in Leverage Capital Calculation	1.0
Risk-Based Capital, Required	$ 1,138	$ 1,146
Risk-Based Capital, Actual	$ 6,888	$ 7,719
Regulatory Capital Ratio, Required	4.00%	4.00%
Regulatory Capital Ratio, Actual	5.31%	5.27%
Regulatory Capital, Required	$ 5,184	$ 5,861
Regulatory Capital, Actual	$ 6,888	$ 7,719
Leverage Ratio, Required	5.00%	5.00%
Federal Home Loan Bank, Leverage Ratio, Actual	7.97%	7.90%
Leverage Capital, Required	$ 6,480	$ 7,326
Leverage Capital, Actual	$ 10,332	$ 11,579