Investment Securities - Additional Information (Details) $ in Millions	Mar. 31, 2016 USD ($) Security	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of sale securities exceeding amortized cost over fair value \| Security	600
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (129)	$ (321)
Difference in amortized cost and fair value of securities that had been in a loss position for 12 months or longer	$ (85)	(165)
Securities held to maturity \| Security	30
Fair value of securities pledged	$ 1,600	1,700
Carrying value of securities pledged	8,500	8,700
Encumbered amount of securities pledged as collateral	10,600	10,600
Fair value of securities pledged, accepted	7	172
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	$ (7)	$ (81)
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	28.00%
Investment Securities Portfolio \| US Treasury and Government
Schedule of Available-for-sale Securities [Line Items]
Percentage of portfolio	91.00%	90.00%
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (94)	$ (234)
Difference in amortized cost and fair value of securities that had been in a loss position for 12 months or longer	(59)	(114)
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	(36)
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	25	22
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(26)	(22)
Difference in amortized cost and fair value of securities that had been in a loss position for 12 months or longer	$ (13)	$ (12)

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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