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Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Income Tax Disclosure [Abstract]        
Income tax expense $ 1,169,000 $ 3,271,000 $ 2,551,000 $ 7,477,000
U.S. federal or state deferred income tax expense or benefits $ 0   $ 0