Investment Securities (Schedule of Investment Securities) (Details) (USD $)
In Millions, unless otherwise specified |
Jun. 30, 2013
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Dec. 31, 2012
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Investment Holdings [Line Items] | ||||||
Total investment securities | $ 4,943 | $ 6,232 | ||||
US Treasury Securities [Member]
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Investment Holdings [Line Items] | ||||||
Total investment securities | 2,068 | 2,460 | ||||
US Government Corporations and Agencies Securities [Member]
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Investment Holdings [Line Items] | ||||||
Total investment securities | 1,570 | 2,233 | ||||
US States and Political Subdivisions Debt Securities [Member]
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Investment Holdings [Line Items] | ||||||
Total investment securities | 24 | 34 | ||||
Total Other Securities [Member]
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Investment Holdings [Line Items] | ||||||
Total investment securities | 1,281 | 1,505 | ||||
Asset-backed Securities, Securitized Loans and Receivables [Member]
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Investment Holdings [Line Items] | ||||||
Total investment securities | 41 | 151 | ||||
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
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Investment Holdings [Line Items] | ||||||
Total investment securities | $ 1,240 | [1] | $ 1,354 | [1] | ||
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