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Related Party Transactions - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Jun. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Related Party Transaction [Line Items]            
Purchase of non-controlling interests $ 50,000 $ 256,000 $ 10,000 $ 306,000 $ 10,000
Partnership And Trust [Member]            
Related Party Transaction [Line Items]            
Purchase of non-controlling interests         $ 306,000 $ 10,000