Capital (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Stock, Par or Stated Value Per Share | $ / shares	$ 100
Number of Subclasses of Capital Stock	2
Minimum Capital Stock Required to be Held by Members as a Percent of Total Assets at Preceeding Fiscal Year End, Subject to Cap and Floor	0.12%
Activity Based Capital Stock Required by Members as a Percent of Total Advances and Mortgage Loans Oustanding as Disclosed in the Statement of Condition	4.00%
Redemption Period Under Bank Capital Plan	5 years
Written Notice Period Required to Repurchase Excess Membership Capital Stock	15 days
Excess Capital	$ 0	$ 0
Net Shares Reclassified to Mandatorily Redeemable Capital Stock, Value	11,000,000	53,000,000	$ 44,000,000
Repayments of Mandatory Redeemable Capital Securities	(60,000,000)	$ (183,000,000)	$ (323,000,000)
Maximum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Federal Home Loan Banks, Membership Requirements, Capital Stock	10,000,000
Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Federal Home Loan Banks, Membership Requirements, Capital Stock	$ 10,000