Capital (Capital Requirements) (Details) $ in Thousands	Sep. 30, 2020 USD ($) numberOfRegulatoryRequirements	Dec. 31, 2019 USD ($)
Banking Regulation, Total Capital [Abstract]
Number of Finance Agency Regulatory Capital Requirements | numberOfRegulatoryRequirements	3
Number Of Subclasses Of Capital Stock	2
Risk-Based Capital, Required	$ 506,766	$ 610,573
Risk-Based Capital, Actual	$ 3,454,571	$ 4,724,586
Total capital-to-asset ratio, Required	4.00%	4.00%
Total capital-to-asset ratio, Actual	5.70%	4.90%
Total regulatory capital, Required	$ 2,417,731	$ 3,828,965
Total regulatory capital, Actual	$ 3,454,571	$ 4,724,586
Leverage ratio - Required	5.00%	5.00%
Leverage ratio, Actual	8.60%	7.40%
Leverage capital, Required	$ 3,022,164	$ 4,786,206
Leverage capital, Actual	$ 5,181,857	$ 7,086,879