Derivatives and Hedging Activities (Offsetting of Derivative Assets and Derivative Liabilities) (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 67	$ 36
Derivative Liability, Fair Value, Gross Liability		97	163
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1],[2]	301	278
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1],[2]	(88)	(146)
Derivative assets		368	314
Derivative liabilities		9	17
Derivative, Collateral, Obligation to Return Securities	[3]	4	0
Derivative, Collateral, Right to Reclaim Securities	[3]	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	[3]	364	314
Derivative Liability, Fair Value, Amount Offset Against Collateral	[3]	9	17
Credit Risk Contract [Member]
Derivatives, Fair Value [Line Items]
Credit Derivative Exposure Net		2	2
Uncleared derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		56	35
Derivative Liability, Fair Value, Gross Liability		95	128
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		(49)	(33)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		(86)	(111)
Derivative assets		7	2
Derivative liabilities		9	17
Derivative, Collateral, Obligation to Return Securities	[3]	4	0
Derivative, Collateral, Right to Reclaim Securities	[3]	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	[3]	3	2
Derivative Liability, Fair Value, Amount Offset Against Collateral	[3]	9	17
Cleared derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		11	1
Derivative Liability, Fair Value, Gross Liability		2	35
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		350	311
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		(2)	(35)
Derivative assets		361	312
Derivative liabilities		0	0
Derivative, Collateral, Obligation to Return Securities	[3]	0	0
Derivative, Collateral, Right to Reclaim Securities	[3]	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	[3]	361	312
Derivative Liability, Fair Value, Amount Offset Against Collateral	[3]	$ 0	$ 0

[1] 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 $411 and $433 as of June 30, 2019 and December 31, 2018, respectively. Cash collateral received and related accrued interest was $22 and $9 as of June 30, 2019 and December 31, 2018, respectively.

[2] 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.

[3] The Bank had net credit exposure of $2 as of June 30, 2019 and December 31, 2018, due to instances where the Bank’s pledged collateral to a counterparty exceeded the Bank’s net derivative liability position.