Quarterly report pursuant to Section 13 or 15(d)

Intangible Assets and Goodwill - Additional Information (Detail)

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Intangible Assets and Goodwill - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Jun. 30, 2017
Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]        
Intangible assets and goodwill impairment     $ 0  
Amortization expense $ 0 $ 0    
Goodwill $ 2,926,000     $ 2,926,000