Quarterly report pursuant to Section 13 or 15(d)

Fair Value Hierarchy Financial Instruments Measured at Fair Value on Recurring Basis (Detail)

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Fair Value Hierarchy Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities $ 39,951 $ 20,002
Long-term investments, at fair value 4,095 4,160
Total 44,046 24,162
U.S. Treasury Bills [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities 39,951 19,998
Mutual Funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities   4
Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities 39,951 20,002
Long-term investments, at fair value 0 0
Total 39,951 20,002
Fair Value, Inputs, Level 1 [Member] | U.S. Treasury Bills [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities 39,951 19,998
Fair Value, Inputs, Level 1 [Member] | Mutual Funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities   4
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities 0 0
Long-term investments, at fair value 0 0
Total 0 0
Fair Value, Inputs, Level 2 [Member] | U.S. Treasury Bills [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities 0 0
Fair Value, Inputs, Level 2 [Member] | Mutual Funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities   0
Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities 0 0
Long-term investments, at fair value 4,095 4,160
Total 4,095 4,160
Fair Value, Inputs, Level 3 [Member] | U.S. Treasury Bills [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Securities $ 0 $ 0