v2.4.0.6
Valuation and Qualifying Accounts (Detail) (Allowance for doubtful accounts of brokerage clients, USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Allowance for doubtful accounts of brokerage clients
      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Year $ 2 [1] $ 1 [1] $ 2 [1]
Charged to Expense 4 [1] 6 [1] 3 [1]
Other   3 [1],[2]  
Written off (5) [1] (8) [1] (4) [1]
Balance at End of Year $ 1 [1] $ 2 [1] $ 1 [1]
[1] Excludes banking-related valuation and qualifying accounts. See "Item 8 - Financial Statements and Supplementary Data - Notes to Consolidated Financial Statements - 7. Loans to Banking Clients and Related Allowance for Loan Losses."
[2] Includes collections of previously written-off accounts.