Investments (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total investments	$ 1,864	$ 1,631
Total trading investments	124	267
Other investments	1,445	1,207
Foreign government debt	103	105
Consolidated Sponsored Investment Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total investments	503	587
Total trading investments	67	214
Other investments	436	373
Trading securities, equity	61
Trading securities, debt	6
Deferred Compensation Plan Mutual Fund Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total trading investments	53	46
Other investments	10	19
Equity And Debt Securities Held In Separate Investment Accounts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total trading investments	$ 4

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

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The total of financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

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Debt securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

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Total common and preferred stock (which is not mandatorily redeemable, redeemable at the option of the holder, or in any other way classified as liability) equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

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