Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Jul. 05, 2017
Basic earnings per common share:
Net income - basic	$ 25,390	$ 21,479	$ 56,406	$ 49,949
Weighted shares outstanding - basic (in shares)	54,965	55,093	54,895	55,084
Basic earnings per share (in dollars per share)	$ 0.46	$ 0.39	$ 1.03	$ 0.91
Diluted earnings per common share:
Net income - basic	$ 25,390	$ 21,479	$ 56,406	$ 49,949
Add: Convertible Notes interest expense, net of tax	2,405	2,415	4,844	5,074
Net income - diluted	$ 27,795	$ 23,894	$ 61,250	$ 55,023
Weighted shares outstanding - basic (in shares)	54,965	55,093	54,895	55,084
Equity-based compensation awards - effect of dilution (in shares)	1,196	974	1,373	1,156
Convertible Notes - effect of dilution (in shares)	26,979	26,978	26,979	28,708
Weighted shares outstanding - diluted (in shares)	83,140	83,045	83,247	84,948
Diluted earnings per share (in dollars per share)	$ 0.33	$ 0.29	$ 0.74	$ 0.65
Potential common shares excluded from the calculation of diluted earnings per common share above (in shares)	1,424	1,676	1,433	1,673
2.375% Convertible Senior Notes, Due 2025 | Senior Notes
Diluted earnings per common share:
Stated interest rate	2.375%	2.375%	2.375%	2.375%
3.750% Convertible Senior Notes, Due 2029 | Senior Notes
Diluted earnings per common share:
Stated interest rate	3.75%	3.75%	3.75%	3.75%
2024 Convertible Notes | Senior Notes
Diluted earnings per common share:
Add: Convertible Notes interest expense, net of tax		$ 0
Potential common shares excluded from the calculation of diluted earnings per common share above (in shares)		3,400
Stated interest rate		2.875%		2.875%	2.875%
Weighted average shares (in shares)				1,700
Conversion price, per share (in dollars per share)		$ 10.00		$ 10.00	$ 10.00
Restricted stock
Diluted earnings per common share:
Potential common shares excluded from the calculation of diluted earnings per common share above (in shares)	1,424	1,676	1,433	1,673