Equity - Schedule of Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Numerator for basic and diluted earnings (loss) per share attributable to common stockholders:
Net income (loss) attributable to common stockholders	$ 25,222	$ (4,229)	$ 31,573	$ 11,541
Denominator:
Basic (in shares)	14,242,076	14,018,099	14,131,050	13,957,706
Effect of diluted securities (in shares)	200,000	0	200,000	0
Diluted (in shares)	14,442,076	14,018,099	14,331,050	13,957,706
Basic earnings (in dollars per share)	$ 1.77	$ (0.30)	$ 2.23	$ 0.83
Diluted earnings (in dollars per share)	$ 1.75	$ (0.30)	$ 2.20	$ 0.83