Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income before income taxes	$ 14,417	$ 6,398	$ 29,222	$ 14,386
Federal income tax rate	21.00%	28.00%	21.00%	28.00%	35.00%
Federal income tax expense at statutory rate	$ 3,028	$ 1,791	$ 6,137	$ 4,028
(Reduction) increases in income taxes resulting from: Tax exempt interest	(148)	(177)	(297)	(349)
(Reduction) increases in income taxes resulting from: State tax, net of federal tax effect	916	461	2,121	970
(Reduction) increases in income taxes resulting from: Incentive stock option compensation expense	28	37	56	72
(Reduction) increases in income taxes resulting from: Income from bank-owned life insurance	(290)	(354)	(579)	(710)
(Reduction) increases in income taxes resulting from: Disqualifying disposition of incentive stock options		(11)		(11)
(Reduction) increases in income taxes resulting from: Non-deductible merger-related expenses		200		200
(Reductions) increases in income taxes resulting from: Other items, net	38	113	690	199
(Reductions) increases in income taxes resulting from: Impact of deferred tax rate adjustment	77	3,069	(820)	3,486
Total income tax expense	$ 3,649	$ 5,129	$ 7,308	$ 7,885
Effective income tax rate	25.31%	80.17%	25.01%	54.81%