Mortgage Banking Activities - Valuation Allowance for Mortgage Servicing Rights (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Mortgage Banking [Abstract]
Balance, beginning of period	$ (569,000)		$ (70,000)	$ (9,000)
Impairment charges	(996,000)	$ (20,000)	(1,495,000)	(20,000)
Recoveries				9,000
Balance, end of period	$ (1,565,000)	$ (20,000)	$ (1,565,000)	$ (20,000)