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Fair Value Measurements - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities, transfers out of Level 3 $ 0  
Gains or losses recognized as result of transfer of securities   $ 0