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Redeemable Noncontrolling Interests and Total Equity (Narrative) (Details) (USD $)
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1 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended | 3 Months Ended | ||||||||||||||||
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Jun. 30, 2009
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Jun. 30, 2011
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Dec. 31, 2007
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Aug. 31, 2010
CIC
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Jun. 30, 2009
CIC
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Dec. 31, 2007
CIC
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Dec. 31, 2012
MSMS
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Dec. 31, 2011
MSMS
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Dec. 31, 2012
Wealth Management JV
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Dec. 31, 2011
Wealth Management JV
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Dec. 31, 2010
Wealth Management JV
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Dec. 31, 2012
Wealth Management JV
Citi
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Sep. 16, 2012
Wealth Management JV
Citi
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Jun. 30, 2011
Series B Preferred Stock
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Dec. 31, 2012
Series B Preferred Stock
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Dec. 31, 2012
Series C Preferred Stock
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Dec. 31, 2011
Series C Preferred Stock
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Mar. 31, 2008
Junior Subordinated Debt
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Mar. 31, 2008
Junior Subordinated Debt
Trust Preferred Securities
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Mar. 31, 2008
Junior Subordinated Debt
Trust Common Securities
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| Treasury Shares | |||||||||||||||||||||||
| Authorized repurchase amount of outstanding common stock | $ 6,000,000,000 | ||||||||||||||||||||||
| Remaining amount under its current share repurchase authorization | 1,600,000,000 | ||||||||||||||||||||||
| MUFG Stock Conversion | |||||||||||||||||||||||
| Preferred stock face value | 1,508,000,000 | 1,508,000,000 | 7,800,000,000 | ||||||||||||||||||||
| Preferred stock carrying value | 1,508,000,000 | 1,508,000,000 | 8,100,000,000 | 408,000,000 | 408,000,000 | ||||||||||||||||||
| Preferred stock dividend rate | 10.00% | 10.00% | 10.00% | ||||||||||||||||||||
| Shares issued upon conversion of preferred stock (in shares) | 385,464,097 | ||||||||||||||||||||||
| Shares issued resulting from the adjustment to the conversion ratio pursuant to the transaction agreement (in shares) | 75,000,000 | ||||||||||||||||||||||
| Adjustment to preferred and common stock conversion ratio | (1,700,000,000) | ||||||||||||||||||||||
| CIC Investment | |||||||||||||||||||||||
| Proceeds from sale of equity unit | 5,579,000,000 | ||||||||||||||||||||||
| Equity unit, stated amount per unit | 1,000 | ||||||||||||||||||||||
| Common stock par value per share | $ 0.01 | $ 0.01 | |||||||||||||||||||||
| Principal amount of debt issued | 24,000,000,000 | 33,000,000,000 | 5,579,173,000 | ||||||||||||||||||||
| Proceeds from issuance of junior subordinated debentures | 5,579,143,000 | 30,000 | |||||||||||||||||||||
| Redemption of equity units and issuances of common stock (in shares) | 116,062,911 | ||||||||||||||||||||||
| Registered public offering (in shares) | 85,890,277 | 0 | 385,000,000 | 116,000,000 | 45,290,576 | ||||||||||||||||||
| Earnings Per Share | |||||||||||||||||||||||
| Conditions of dilution of net income per share | Dilution of net income per share occurred (i) in reporting periods when the average closing price of common shares was over $57.6840 per share or (ii) in reporting periods when the average closing price of common shares for a reporting period was between $48.0700 and $57.6840 and was greater than the average market price for the last 20 days ending three days prior to the end of such reporting period. | ||||||||||||||||||||||
| Earnings per share threshold for Equity Unit holders (per share) | $ 0.27 | ||||||||||||||||||||||
| Nonredeemable Noncontrolling Interests | |||||||||||||||||||||||
| Noncontrolling interest in joint ventures, percentage | 35.00% | 49.00% | |||||||||||||||||||||
| Distributions to noncontrolling interests | $ 151,000,000 | $ 416,000,000 | $ 97,000,000 | $ 346,000,000 | $ 306,000,000 | ||||||||||||||||||