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Fair Value Measurements - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Fair Value Option Quantitative Disclosures [Line Items]          
Transfers between Level 1, 2 and 3 in fair value measurement hierarchy $ 0 $ 0 $ 0 $ 0  
Unfunded Commitments 9,183,000   9,183,000   $ 9,183,000
EGCP III [Member]          
Fair Value Option Quantitative Disclosures [Line Items]          
Unfunded Commitments $ 8,613,000   $ 8,613,000    
End of the investment period     Oct. 12, 2016    
Remaining obligation date     Oct. 12, 2023