Conversion - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended		24 Months Ended
	Jul. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Jul. 01, 2016
Plan Of Conversion [Line Items]
Common stock, shares issued		5,868,726	0	5,868,726	5,686,750
Share issued, price per share					$ 10.00
Proceeds from issuance of common stock	$ 56,867,500	$ 56,868,000
Direct cost of stock offering		$ 2,004,000	$ 321,000	$ 2,325,000
Contribution to Randolph Charitable Foundation Inc, shares		181,976
Contribution to Randolph Charitable Foundation Inc, cash		$ 455,000
Contribution to Randolph Charitable Foundation Inc, expense recognized		$ 2,274,700
ESOP [Member]
Plan Of Conversion [Line Items]
Common stock, shares issued					469,498
Loan repayment period	25 years