Deposits and Borrowing - Additional Information (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Banking and Thrift [Abstract]
Time deposit threshold amount	$ 250,000
Time deposits of $250,000 or more totaled	130,385,000	$ 190,386,000
Deposits received from related parties	114,513,000	89,006,000
Advances from Federal Home Loan Bank of Dallas, maturing during 2017	$ 75,000,000	299,020,000
Advances from Federal Home Loan Bank of Dallas, maturing during 2018		$ 299,020,000
Interest rate on advance	0.46%	0.31%