Employee Stock Ownership Plan - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Loan repaid term		25 years
Interest rate	3.50%
Number of allocated shares	18,780	18,780
Annual allocation of shares, expiration year		2040
ESOP expense | $		$ 257,000
Unallocated shares	450,718	450,718
Unallocated shares, value | $	$ 7,266,000	$ 7,266,000
Common Stock [Member]
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Sale of stock, price per share | $ / shares	$ 10.00	$ 10.00
The Randolph Savings Charitable Foundation, Inc. [Member]
Employee Stock Ownership Plan E S O P Disclosures [Line Items]
Sale of share in employee stock ownership plan		469,498