Netting Arrangements Narratives (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Fair value of non-cash collateral we pledged	$ 1,300,000,000	$ 197,000,000
Fair value of non-cash collateral received	51,200,000,000	38,000,000,000
Fair value of non-cash collateral received that could be sold or repledged	45,500,000,000	36,200,000,000
Fair value of underlying collateral that was sold or repledged	0	0
Derivative assets not subject to an enforceable master netting arrangement	33,000,000	28,000,000
Derivative liabilities not subject to an enforceable master netting arrangement	2,000,000	2,000,000
Cash and cash equivalents [Member]
Derivative [Line Items]
Securities purchased under agreements to resell or similar agreements	$ 20,700,000,000	$ 10,600,000,000