Income Taxes - Schedule of Provision for Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Current:
Federal income tax									$ 1,961	$ 102	$ 244
State income tax									384	0	0
Total current									2,345	102	244
Deferred:
Federal income tax									(3,917)	(3,286)	4,538
State income tax									1,962	(662)	739
Total deferred									(1,955)	(3,948)	5,277
Provision (benefit) for income taxes	$ (284)	$ 4,941	$ 8,150	$ (12,417)	$ (10,559)	$ 3,665	$ 4,321	$ (1,273)	$ 390	$ (3,846)	$ 5,521