Accumulated Other Comprehensive Income (Components of Other Comprehensive (Loss) Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Change in net unrealized gain on Securities available for sale:
Net unrealized gain	$ 107	$ 159
Other reclassifications included in other revenue		(1)
Change in net unrealized gain on securities available for sale	107	158
Other comprehensive income, before tax	107	158
Change in net unrealized gain on Securities available for sale:
Net unrealized gain	(41)	(59)
Change in net unrealized gain on securities available for sale	(41)	(59)
Other comprehensive (loss) income, tax effect	(41)us-gaap_OtherComprehensiveIncomeLossTax	(59)us-gaap_OtherComprehensiveIncomeLossTax
Change in net unrealized gain on securities available for sale:
Net unrealized gain	66	100
Other reclassifications included in other revenue		(1)
Change in net unrealized gain on securities available for sale	66	99
Other comprehensive income, net of tax	$ 66	$ 99

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