Basis of Presentation - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
12 Months Ended |
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Dec. 31, 2011
|
|
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] | |
Proceeds from sales of businesses | $ 27.1 |
Securities Industry
|
|
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] | |
Number of businesses sold | 2 |
Discontinued Operations [Member]
|
|
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] | |
Number of businesses sold | 3 |