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Organization and Nature of Operations (Details) (USD $)
In Trillions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
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Organization And Basis Of Presentation [Line Items]  
Operations in number of continents 6
Total number of U.S. listed companies 2,568
Approximate combined market capitalization, U.S. $ 5.6
Total number of listed companies within Nordic and Baltic exchanges 752
Approximate combined market capitalization $ 1.1