Investment Securities - Additional Information (Details) $ in Millions	Dec. 31, 2015 USD ($) Security	Dec. 31, 2014 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of sale securities exceeding amortized cost over fair value \| Security	700
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (321)	$ (237)
Difference in amortized cost and fair value of securities that had been in a loss position for 12 months or longer	$ (165)	(206)
Securities held to maturity \| Security	100
Fair value of securities pledged	$ 1,700	3,500
Carrying value of securities pledged	8,700	9,000
Encumbered amount of securities pledged as collateral	10,600	10,600
Fair value of securities pledged, accepted	172	91
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	$ (81)	$ (6)
Non-agency RMBS and CMBS, Non-agency ABS and Other Securities \| Gross Unrealized Losses on Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Percentage of portfolio	17.00%
Investment Securities Portfolio \| US Treasury and Government
Schedule of Available-for-sale Securities [Line Items]
Percentage of portfolio	90.00%	86.00%
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (234)	$ (118)
Difference in amortized cost and fair value of securities that had been in a loss position for 12 months or longer	(114)	(94)
Non-agency RMBS and CMBS, Non-agency ABS and Other Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(53)
Non-Agency \| Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	22	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(22)	(13)
Difference in amortized cost and fair value of securities that had been in a loss position for 12 months or longer	$ (12)	$ (4)

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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Amount of obligation to return securities collateral under master netting arrangements that have not been offset against derivative assets.

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