Statements of Condition (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2020		Dec. 31, 2019
Statement of Financial Position [Abstract]
Held-to-maturity securities - pledged as collateral that may be repledged (a)	$ 0		$ 92
Allowance for credit losses - held-to-maturity securities	3,768	[1]	0
Allowance for credit losses - mortgage loans held for portfolio	3,500		500
Fair value of held-to-maturity securities	$ 733,970		$ 1,035,410
Common Class B [Member]
Common Stock, Class B, putable shares issued	22,663		18,691
Common Stock, Class B, putable par value per share	$ 100		$ 100
Common Stock, Class B, putable shares outstanding	22,663		18,691

[1] With the adoption of changes to accounting standards on credit impairment on January 1, 2020, the other-than-temporary impairment approach was replaced with an allowance for credit loss; however, other-than-temporary impairment remains for those securities that had credit impairment prior to the adoption date. See Note 2 — Summary of Significant Accounting Policies and Note 3 — Recently Issued and Adopted Accounting Guidance for further information.