Affordable Housing Program Schedule of Change in AHP Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Affordable Housing Program [Roll Forward]
AHP Obligation, beginning of the period	$ 182	$ 204	$ 205
AHP Assessment	38	43	45
AHP Voluntary Contributions	2	3	7
AHP Grant Payments	(70)	(68)	(53)
AHP Obligation, end of the period	$ 152	$ 182	$ 204