Contracts Accounted for as Credit Derivatives - Narrative (Details)		3 Months Ended	12 Months Ended
		Dec. 31, 2014 USD ($) Transaction	Dec. 31, 2016 USD ($) Transaction Counterparty	Dec. 31, 2015 USD ($) Transaction Counterparty	Dec. 31, 2014 USD ($) Transaction	May 31, 2016 USD ($)
Credit Derivatives
Estimated remaining weighted average life of credit derivatives (in years)			5 years 3 months 6 days	5 years 5 months
Net par outstanding	[1]		$ 16,997,000,000	$ 25,594,000,000
Fair value gains				49,000,000
Gain from narrowing of spreads		$ 346,000,000
Collateral agreed to be posted			$ 116,000,000	305,000,000
Market value collateralized debt obligations of corporate obligations [Member]
Credit Derivatives
Maximum average obligor size (as a percent)			1.00%
Maximum exposure of one industry (as a percent)			10.00%
Net par outstanding			$ 10,425,000,000	17,523,000,000
Other pooled infrastructure [Member]
Credit Derivatives
Net par outstanding			$ 1,500,000,000
Pooled infrastructure [Member]
Credit Derivatives
Number of transactions | Transaction			1
Remaining other CDS [Member]
Credit Derivatives
Net par outstanding			$ 3,900,000,000
Commercial Mortgage Backed Securities (CMBS) [Member]
Credit Derivatives
Net par outstanding			0	530,000,000
Unrealized fair value gain on termination of transactions				41,000,000
Triple-X Life Insurance Transaction [Member]
Credit Derivatives
Unrealized fair value gain on termination of transactions				99,000,000
Collateral Debt Obligations, Collateral Requirement [Member]
Credit Derivatives
Amount of par subject to collateral for which the amount of collateral is capped			700,000,000	3,800,000,000		$ 0
Derivative, reduction of notional amount			3,100,000,000
Collateral Debt Obligations, Collateral Cap Negotiated [Member]
Credit Derivatives
Amount of par subject to collateral for which the amount of collateral is capped			516,000,000
Collateral Debt Obligations, No Cap Negotiated [Member]
Credit Derivatives
Amount of par subject to collateral for which the amount of collateral is capped			500,000,000
Notional amount subject to collateral based on movements in the mark-to-market valuation of the underlying exposure			174,000,000	221,000,000
Collateral agreed to be posted			116,000,000	305,000,000
Collateral posted, based on mark-to-market valuation			$ 16,000,000	$ 23,000,000
Counterparties involved in eliminating credit derivatives | Counterparty			1
Credit derivative contract, gross par terminated			$ 183,000,000
Terminated credit derivatives, collateral already posted			73,000,000
Option Adjustable Rate Mortgage and Alt-A Mortgage [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (RMBS) [Member]
Credit Derivatives
Unrealized fair value gain on termination of transactions					$ 543,000,000
Alt-A [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (RMBS) [Member]
Credit Derivatives
Counterparties involved in transaction termination | Counterparty				1
Number of transactions terminated | Transaction		3		5	3
Unrealized fair value gain on termination of transactions				$ 213,000,000
Collateralized Loan Obligations and Collateral Bond Obligations [Member] | Market value collateralized debt obligations of corporate obligations [Member]
Credit Derivatives
Net par outstanding			$ 2,022,000,000	5,873,000,000
Unrealized fair value gain on termination of transactions				$ 99,000,000
Option Adjustable Rate Mortgage [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (RMBS) [Member]
Credit Derivatives
Number of transactions terminated | Transaction		1			1

[1] The December 31, 2016 total amount includes $1.7 billion net par outstanding of credit derivatives from CIFG Acquisition.