Capital (Regulatory Capital Requirements) (Details) $ in Millions	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Banking Regulation, Total Capital [Abstract]
Number of Finance Agency Regulatory Capital Requirements	3
Federal Home Loan Bank, Risk-Based Capital, Required	$ 673	$ 1,138
Federal Home Loan Bank, Risk-Based Capital, Actual	6,948	6,888
Federal Home Loan Bank, Regulatory Capital, Required	5,043	5,184
Federal Home Loan Bank, Regulatory Capital, Actual	6,948	6,888
Federal Home Loan Bank, Leverage Capital, Required	6,303	6,480
Federal Home Loan Bank, Leverage Capital, Actual	$ 10,421	$ 10,332
Regulatory Capital Ratio, Required	4.00%	4.00%
Federal Home Loan Bank, Regulatory Capital Ratio, Actual	5.51%	5.31%
Federal Home Loan Bank, Capital Stock to Assets, Required	2.00%
Federal Home Loan Bank, Capital Stock to Assets, Actual	3.72%
Leverage Ratio, Required	5.00%	5.00%
Federal Home Loan Bank, Leverage Ratio, Actual	8.27%	7.97%
Weight Applied to Permanent Capital in Computing Leverage Ratio	1.5
Weight Applied to Nonpermanent Capital in Computing Leverage Ratio	1.0