Commitments and Contingencies - Summary of Company's Commitments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 431,678	$ 293,517	$ 243,163
Unused lines of credit	51,834	49,567	41,908
Financial standby letters of credit	10,535	9,683	8,392
Mortgage interest rate lock commitments	$ 91,977	$ 38,868	$ 70,854