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FINANCIAL INSTRUMENTS, OFF-BALANCE SHEET RISKS AND CONTINGENCIES (Additional Information) (Detail) - USD ($)
Mar. 31, 2017
Dec. 31, 2016
Money Market Funds [Member]    
Loss Contingencies [Line Items]    
Deposits in domestic and foreign financial institutions, including cash investments in money market funds $ 700,000,001 $ 748,000,001
US Treasury Securities [Member]    
Loss Contingencies [Line Items]    
Deposits in domestic and foreign financial institutions, including cash investments in money market funds $ 2,286,664,001 $ 2,422,382,750