Derivatives and Hedging Activities (Offsetting of Derivative Assets and Derivative Liabilities) (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Total Derivative Assets and Derivative Liabilities		$ 62	$ 33
Derivative Asset, Fair Value, Amount Offset Against Collateral		705	414
Netting Adjustments and Cash Collateral-Derivative Liability	[1]	(1,055)	(384)
Derivative Assets and Derivative Liabilities		0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral		0	0
Uncleared derivatives
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Recognized Amount		15	34
Derivative Asset Fair Value Gross Liability and Right To Reclaim Cash Offset		20	(16)
Derivative Asset, Not Subject to Master Netting Arrangement		3
Total Derivative Assets and Derivative Liabilities		38	18
Derivative Asset, Noncash collateral not offset that can be sold or repledged		0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		38	18
Derivative Liability, Fair Value, Gross Recognized Amount		1,041	382
Netting Adjustments and Cash Collateral-Derivative Liability		(1,041)	(382)
Derivative Liability, Not Subject to Master Netting Arrangement		0
Derivative Assets and Derivative Liabilities		0	0
Derivative Liability, Noncash collateral not offset that can be sold or repledged		0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral		0	0
Cleared derivatives
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Recognized Amount		27	10
Derivative Asset Fair Value Gross Liability and Right To Reclaim Cash Offset		(3)	5
Derivative Asset, Not Subject to Master Netting Arrangement		0
Total Derivative Assets and Derivative Liabilities		24	15
Derivative Asset, Noncash collateral not offset that can be sold or repledged		(643)	(381)
Derivative Asset, Fair Value, Amount Offset Against Collateral		667	396
Derivative Liability, Fair Value, Gross Recognized Amount		14	2
Netting Adjustments and Cash Collateral-Derivative Liability		(14)	(2)
Derivative Liability, Not Subject to Master Netting Arrangement		0
Derivative Assets and Derivative Liabilities		0	0
Derivative Liability, Noncash collateral not offset that can be sold or repledged		0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral		$ 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 $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.