Earnings per Share (EPS) and Common Stock - Earnings per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share And Common Stock [Abstract]
Net income	$ 70,476	$ 51,203	$ 206,244	$ 183,980
Weighted-average shares outstanding—Basic	117,073	116,934	117,114	116,702
Dilutive effect of restricted stock units	895	1,677	983	1,479
Weighted-average shares outstanding—Diluted	117,968	118,611	118,097	118,181
Earnings per share—Basic	$ 0.60	$ 0.44	$ 1.76	$ 1.58
Earnings per share—Diluted	$ 0.60	$ 0.43	$ 1.75	$ 1.56