EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income, as reported	$ 96,035	$ 111,312	$ 149,809	$ 81,045	$ 207,347	$ 230,854
Basic earnings per share
Weighted average shares of common stock outstanding-basic (in shares)	96,068,000		96,248,000		96,006,000	96,181,000
Basic earnings per common share (usd per share)	$ 1.00		$ 1.56		$ 2.16	$ 2.40
Diluted earnings per share
Weighted average shares of common stock outstanding-basic (in shares)	96,068,000		96,248,000		96,006,000	96,181,000
Incremental shares (in shares)	448,000		370,000		474,000	417,000
Weighted average shares of common stock outstanding-diluted (in shares)	96,516,000		96,618,000		96,480,000	96,598,000
Diluted earnings per common share (usd per share)	$ 1.00		$ 1.55		$ 2.15	$ 2.39
Share-based Payment Arrangement
Diluted earnings per share
Anti-dilutive shares excluded from the calculation of diluted earnings per share (in shares)			24,101			65,334