UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 84,831	$ 164,040	$ 180,004	$ 261,185
Other comprehensive income, net of income taxes:
Net change related to employee benefit plans, net of income taxes of $(39.5) thousand and $(79.0) thousand for the three and six months ended March 31, 2024, respectively, and $(75.0) thousand and $(150.1) thousand for the three and six months ended March 31, 2023, respectively	134	256	268	512
Other comprehensive income	134	256	268	512
Comprehensive income	$ 84,965	$ 164,296	$ 180,272	$ 261,697