Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Additional Information (Detail)

v3.8.0.1
Fair Value Measurements - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Fair Value Disclosures [Abstract]      
Assets at fair value on recurring basis $ 0    
Liabilities at fair value on recurring basis 0    
Fair value of assets transfers in or out, level 1 to level 2 0 $ 0 $ 0
Fair value of assets transfers in or out, level 2 to level 1 0 0 0
Fair value, asset transfers into Level 3 0 0 0
Fair value, asset transfers out of Level 3 $ 0 $ 0 $ 0