Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Federal									$ 3,456	$ 2,154	$ 1,505
State										16
Total current taxes									3,456	2,170	1,505
Deferred income tax benefit									(873)	784	1,386
Actual tax expense and effective rate, Amount	$ 499	$ 792	$ 726	$ 566	$ 636	$ 618	$ 848	$ 852	$ 2,583	$ 2,954	$ 2,891