Earnings per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net (loss) income	$ (740,618)	$ 44,511	$ (697,344)	$ 90,297
Weighted average common shares outstanding (in shares)	55,906,002	56,994,817	56,141,816	57,484,838
Dilutive effect of stock based compensation (in shares)	0	79,857	0	72,146
Weighted average common shares outstanding for diluted earnings per share calculation (in shares)	55,906,002	57,074,674	56,141,816	57,556,984
Basic earnings per share (in dollars per share)	$ (13.25)	$ 0.78	$ (12.42)	$ 1.57
Diluted earnings per share (in dollars per share)	$ (13.25)	$ 0.78	$ (12.42)	$ 1.57