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Commitments and Contingencies - Credit Extension Commitments (Details) (USD $)
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Sep. 30, 2013
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Jun. 30, 2013
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Dec. 31, 2012
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Sep. 30, 2012
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Jun. 30, 2012
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Dec. 31, 2011
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| Credit Extension Commitments [Abstract] | ||||||||||||
| Legally Binding Unfunded Commitments Syndicated | $ 21,000,000,000 | $ 23,900,000,000 | ||||||||||
| Carrying Amount Credit Extension Commitments Syndicated | 499,000,000 | 534,000,000 | ||||||||||
| Deferred revenue related to binding unfunded lending commitments | 19,000,000 | 21,000,000 | ||||||||||
| Other Liabilities Reserve For Unfunded Lending Commitments | 480,000,000 | 474,000,000 | 513,000,000 | 518,000,000 | 574,000,000 | 714,000,000 | ||||||
| Notional Amount Of Credit Extension Commitments Under Fair Value Option | 14,700,000,000 | 18,300,000,000 | ||||||||||
| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 491,494,000,000 | 530,383,000,000 | ||||||||||
| Expire After One Year Through Three Years | 128,890,000,000 | 108,926,000,000 | ||||||||||
| Expire After Three Years Through Five Years | 158,222,000,000 | 157,253,000,000 | ||||||||||
| Expire After Five Years | 41,438,000,000 | 47,095,000,000 | ||||||||||
| Notional Amount Of Credit Extension Commitments | 820,044,000,000 | 843,657,000,000 | ||||||||||
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External Credit Rating, Investment Grade [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Notional amount of Sblcs and financial guarantees | 28,600,000,000 | 31,500,000,000 | ||||||||||
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External Credit Rating, Non Investment Grade [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Notional amount of Sblcs and financial guarantees | 10,100,000,000 | 11,600,000,000 | ||||||||||
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Legally Binding Commitments [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 112,458,000,000 | 132,521,000,000 | ||||||||||
| Expire After One Year Through Three Years | 128,890,000,000 | 108,926,000,000 | ||||||||||
| Expire After Three Years Through Five Years | 158,222,000,000 | 157,253,000,000 | ||||||||||
| Expire After Five Years | 41,438,000,000 | 47,095,000,000 | ||||||||||
| Notional Amount Of Credit Extension Commitments | 441,008,000,000 | 445,795,000,000 | ||||||||||
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Loan Commitments [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 84,608,000,000 | 103,791,000,000 | ||||||||||
| Expire After One Year Through Three Years | 102,677,000,000 | 83,885,000,000 | ||||||||||
| Expire After Three Years Through Five Years | 133,045,000,000 | 130,805,000,000 | ||||||||||
| Expire After Five Years | 22,056,000,000 | 19,942,000,000 | ||||||||||
| Notional Amount Of Credit Extension Commitments | 342,386,000,000 | 338,423,000,000 | ||||||||||
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Home Equity [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 3,711,000,000 | 2,134,000,000 | ||||||||||
| Expire After One Year Through Three Years | 16,398,000,000 | 13,584,000,000 | ||||||||||
| Expire After Three Years Through Five Years | 21,976,000,000 | 23,344,000,000 | ||||||||||
| Expire After Five Years | 14,631,000,000 | 21,856,000,000 | ||||||||||
| Notional Amount Of Credit Extension Commitments | 56,716,000,000 | 60,918,000,000 | ||||||||||
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Financial Standby Letter Of Credit And Financial Guarantee [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 22,536,000,000 | [1] | 24,593,000,000 | [1] | ||||||||
| Expire After One Year Through Three Years | 9,739,000,000 | [1] | 11,387,000,000 | [1] | ||||||||
| Expire After Three Years Through Five Years | 2,437,000,000 | [1] | 3,094,000,000 | [1] | ||||||||
| Expire After Five Years | 4,461,000,000 | [1] | 4,751,000,000 | [1] | ||||||||
| Notional Amount Of Credit Extension Commitments | 39,173,000,000 | [1] | 43,825,000,000 | [1] | ||||||||
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Financial Standby Letter Of Credit And Financial Guarantee [Member] | Consumer Letter of Credit [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Notional Amount Of Credit Extension Commitments | 537,000,000 | 669,000,000 | ||||||||||
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Letter of Credit [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 1,603,000,000 | 2,003,000,000 | ||||||||||
| Expire After One Year Through Three Years | 76,000,000 | 70,000,000 | ||||||||||
| Expire After Three Years Through Five Years | 764,000,000 | 10,000,000 | ||||||||||
| Expire After Five Years | 290,000,000 | 546,000,000 | ||||||||||
| Notional Amount Of Credit Extension Commitments | 2,733,000,000 | 2,629,000,000 | ||||||||||
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Credit Card Lines [Member]
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| Notional Amount of Credit Extension Commitments [Abstract] | ||||||||||||
| Expire in One Year or Less | 379,036,000,000 | [2] | 397,862,000,000 | [2] | ||||||||
| Notional Amount Of Credit Extension Commitments | 379,036,000,000 | [2] | 397,862,000,000 | [2] | ||||||||
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Unfunded loan commitments [Member]
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| Credit Extension Commitments [Abstract] | ||||||||||||
| Fair Value Carrying Amount Liabilities | $ 412,000,000 | $ 528,000,000 | ||||||||||
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