Reserve for Unfunded Commitments - Summary of Activity in Reserve for Unfunded Commitments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Balance at beginning of period	$ 2,599	$ 2,883	$ 2,719	$ 2,475
Change in reserve for unfunded commitments	390	25	270	433
Balance at end of period	$ 2,989	$ 2,908	$ 2,989	$ 2,908