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Intangible Assets - Reconciliation of Intangible Assets (Detail) - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Dec. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Jun. 30, 2018
Dec. 31, 2017
Jun. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]            
Gross carrying amount at beginning of period $ 68,322 $ 68,322        
Gross carrying amount at end of period 68,322 68,322 $ 68,322 $ 68,322    
Accumulated amortization at beginning of period (36,964) (38,193)        
Amortization expense (1,229) (2,460) (981) (981) $ (724) $ (724)
Accumulated amortization at end of period (38,193) (40,653) (38,193) $ (36,964)    
Net book value at end of period $ 30,129 $ 27,669 $ 30,129