Fair Value (Carrying Value and Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
Assets
Cash and due from banks		$ 328	$ 118
Trading securities		4,319	1,766
Available-for-sale (AFS) securities	[1]	16,175	15,495
HTM securities, Carrying Value	[2]	6,864	7,545
HTM Securities, Fair Value		6,867	7,566
Accrued interest receivable		139	139
Derivative assets, net		62	33
Derivative Assets		45	44
Derivative Asset, Netting adjustments	[3]	(17)	11
Liabilities
Mandatorily redeemable capital stock		83	138		$ 227	$ 227
Accrued interest payable		121	164
Derivative liabilities, net		0	0
Derivative Liabilities		1,055	384
Derivative Liability, Netting adjustments	[3]	(1,055)	(384)
Net Carrying Value
Assets
Cash and due from banks		328	118
Interest-bearing deposits		3,577	2,269
Securities purchased under agreements to resell		2,000	7,000
Federal funds sold		10,081	3,562
Trading securities		4,319	1,766
Available-for-sale (AFS) securities		16,175	15,495
HTM securities, Carrying Value		6,864	7,545
Advances		77,872	65,374
Mortgage loans held for portfolio, net of allowance for credit losses on mortgage loans		3,239	3,314
Accrued interest receivable		139	139
Derivative assets, net	[4]	62	33
Other assets	[5]	16	19
Liabilities
Deposits		721	537
Total consolidated obligations		117,039	98,748
Mandatorily redeemable capital stock		83	138
Accrued interest payable		121	164
Derivative liabilities, net	[4]	0	0
Estimated Fair Value
Assets
Cash and due from banks		328	118
Interest-bearing deposits		3,577	2,269
Securities purchased under agreements to resell		2,000	7,000
Federal funds sold		10,081	3,562
Trading securities		4,319	1,766
Available-for-sale (AFS) securities		16,175	15,495
HTM Securities, Fair Value		6,867	7,566
Advances		77,951	65,492
Mortgage loans held for portfolio, net of allowance for credit losses on mortgage loans		3,320	3,332
Accrued interest receivable		139	139
Derivative assets, net	[4]	62	33
Other assets	[5]	16	19
Liabilities
Deposits		721	537
Total consolidated obligations		117,138	98,764
Mandatorily redeemable capital stock		83	138
Accrued interest payable		121	164
Derivative liabilities, net	[4]	0	0
Level 1
Assets
Cash and due from banks		328	118
Interest-bearing deposits		3,577	2,269
Securities purchased under agreements to resell		0	0
Federal funds sold		0	0
Trading securities		0	0
Available-for-sale (AFS) securities		0	0
HTM Securities, Fair Value		0	0
Advances		0	0
Mortgage loans held for portfolio, net of allowance for credit losses on mortgage loans		0	0
Accrued interest receivable		0	0
Derivative Assets		0	0	[4]
Other assets	[5]	16	19
Liabilities
Deposits		0	0
Total consolidated obligations		0	0
Mandatorily redeemable capital stock		83	138
Accrued interest payable		0	0
Derivative Liabilities		0		[4]
Level 2
Assets
Cash and due from banks		0	0
Interest-bearing deposits		0	0
Securities purchased under agreements to resell		2,000	7,000
Federal funds sold		10,081	3,562
Trading securities		4,319	1,766
Available-for-sale (AFS) securities		13,949	12,898
HTM Securities, Fair Value		6,539	7,181
Advances		77,951	65,492
Mortgage loans held for portfolio, net of allowance for credit losses on mortgage loans		3,320	3,332
Accrued interest receivable		139	139
Derivative Assets	[4]	45	44
Derivative Asset, Netting adjustments	[4]	17	(11)
Other assets	[5]	0	0
Liabilities
Deposits		721	537
Total consolidated obligations		117,138	98,764
Mandatorily redeemable capital stock		0	0
Accrued interest payable		121	164
Derivative Liabilities	[4]	1,055	384
Derivative Liability, Netting adjustments	[4]	(1,055)	(384)
Level 3
Assets
Cash and due from banks		0	0
Interest-bearing deposits		0	0
Securities purchased under agreements to resell		0	0
Federal funds sold		0	0
Trading securities		0	0
Available-for-sale (AFS) securities		2,226	2,597
HTM Securities, Fair Value		328	385
Advances		0	0
Mortgage loans held for portfolio, net of allowance for credit losses on mortgage loans		0	0
Accrued interest receivable		0	0
Derivative Assets		0	0	[4]
Other assets	[5]	0	0
Liabilities
Deposits		0	0
Total consolidated obligations		0	0
Mandatorily redeemable capital stock		0	0
Accrued interest payable		0	0
Derivative Liabilities		0	0	[4]
Standby letters of credit | Net Carrying Value
Other
Other commitments		33	32
Standby letters of credit | Estimated Fair Value
Other
Other commitments		33	32
Standby letters of credit | Level 1
Other
Other commitments		0	0
Standby letters of credit | Level 2
Other
Other commitments		33	32
Standby letters of credit | Level 3
Other
Other commitments		0	0
Discount notes | Net Carrying Value
Liabilities
Discount notes		39,102	27,376
Discount notes | Estimated Fair Value
Liabilities
Discount notes		39,146	27,378
Discount notes | Level 1
Liabilities
Discount notes		0	0
Discount notes | Level 2
Liabilities
Discount notes		39,146	27,378
Discount notes | Level 3
Liabilities
Discount notes		0	0
Bonds
Liabilities
Bonds		254	337
Bonds | Net Carrying Value
Liabilities
Bonds		77,937	71,372
Bonds | Estimated Fair Value
Liabilities
Bonds		77,992	71,386
Bonds | Level 1
Liabilities
Bonds		0	0
Bonds | Level 2
Liabilities
Bonds		77,992	71,386
Bonds | Level 3
Liabilities
Bonds		$ 0	$ 0

[1] At March 31, 2020, $643 of these securities were pledged as collateral that may be repledged. At December 31, 2019, $381 of these securities were pledged as collateral that may be repledged.

[2] At March 31, 2020, and December 31, 2019, none of these securities were pledged as collateral that may be repledged.

[3] Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions, and also cash collateral and related accrued interest held or placed with the same clearing agents and/or counterparty. Cash collateral posted and related accrued interest was $1,082 and $378 at March 31, 2020, and December 31, 2019, respectively. Cash collateral received and related accrued interest was $9 and $5 at March 31, 2020, and December 31, 2019, respectively.

[4] Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions, and also cash collateral and related accrued interest held or placed with the same clearing agents and/or counterparty.

[5] Represents publicly traded mutual funds held in a grantor trust.