Netting Arrangements Narratives (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative assets not subject to an enforceable master netting arrangement	$ 28,000,000	$ 28,000,000
Derivative liabilities not subject to an enforceable master netting arrangement	2,000,000	1,000,000
Cash and cash equivalents [Member]
Derivative [Line Items]
Securities purchased under agreements to resell	10,600,000,000	16,600,000,000
Securities purchased under agreements to resell [Member]
Derivative [Line Items]
Fair value of non-cash collateral accepted	38,000,000,000	47,600,000,000
Fair value of non-cash collateral accepted that could be sold or repledged	36,200,000,000	41,900,000,000
Fair value of securities accepted as collateral that have been sold or repledged	0	0
Securities sold under agreements to repurchase [Member]
Derivative [Line Items]
Fair value of non-cash collateral pledged for securities sold under agreements to repurchase	62,000,000	50,000,000
Cleared Risk Management Derivatives [Member]
Derivative [Line Items]
Fair value of non-cash collateral pledged for cleared risk management derivatives	135,000,000
OTC Risk Management Derivatives [Member]
Derivative [Line Items]
Fair value of non-cash collateral accepted	$ 37,000,000	$ 51,000,000