|
Payables to Brokerage Clients - Additional Information (Detail) (USD $)
In Billions, unless otherwise specified |
12 Months Ended | |
|---|---|---|
|
Dec. 31, 2012
|
Dec. 31, 2011
|
|
| Payables to Brokerage Clients Disclosure [Line Items] | ||
| Cash balances in interest-bearing brokerage client accounts | $ 32.6 | $ 30.6 |
| Average rate paid on cash balances in interest-bearing brokerage client accounts | 0.01% | 0.01% |