Affordable Housing Program Narratives (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Affordable Housing Program [Roll Forward]
Balance at beginning of period	$ 86,131	$ 83,965	$ 83,965
AHP expense for the period	4,636	6,085	21,302
AHP direct grant disbursements	(4,672)	$ (2,281)	(15,723)
AHP subsidy for AHP advance disbursements	(1,026)		(3,450)
Return of previously disbursed grants and subsidies	13		37
Balance at end of period	$ 85,082		$ 86,131