Investment Securities - Additional Information on Securities in a Continuous Loss Position (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) Security	Dec. 31, 2016 USD ($) Security
Schedule of Available-for-sale Securities
Number of debt securities with unrealized losses | Security	393	397
Debt securities with unrealized losses (percentage of amortized cost)	1.53%	1.79%
Number of securities | Security	31	31
Amortized cost basis	$ 110,803	$ 116,886
Unrealized loss	$ 2,818	$ 3,164
Fannie Mae, Freddie Mac, or Ginnie Mae
Schedule of Available-for-sale Securities
Number of securities | Security	28	28
Amortized cost basis	$ 107,140	$ 112,983
Unrealized loss	$ 2,769	$ 3,111
Political Subdivisions
Schedule of Available-for-sale Securities
Number of securities | Security	0	0
Amortized cost basis	$ 0	$ 0
Unrealized loss	$ 0	$ 0
Other
Schedule of Available-for-sale Securities
Number of securities | Security	3	3
Amortized cost basis	$ 3,663	$ 3,903
Unrealized loss	$ 49	$ 53