Income Taxes - Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Federal:
Current	$ 60		$ 90
Deferred	1,021	$ (162)	1,250	$ (13,789)
Gross Federal	1,081	(162)	1,340	(13,789)
State:
Current	192	149	202	308
Deferred	80	19	80	(90)
Gross State	272	168	282	218
Income tax expense (benefit)	$ 1,353	$ 6	$ 1,622	$ (13,571)