v3.26.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]        
Balance as of beginning of period $ 2,648,557 $ 2,477,907 $ 2,391,666 $ 2,200,443
Amounts reclassified from accumulated other comprehensive loss, net of tax 257 68 773 203
Balance as of end of period 2,643,460 2,423,616 2,643,460 2,423,616
Tax on amounts reclassified from accumulated other comprehensive loss (78) (21) (234) (64)
Total        
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]        
Balance as of beginning of period (10,947) (6,386) (11,463) (6,521)
Balance as of end of period (10,690) (6,318) (10,690) (6,318)
Cash Flow Hedges        
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]        
Balance as of beginning of period (4,637) (5,689) (5,163) (6,215)
Amounts reclassified from accumulated other comprehensive loss, net of tax 264 264 790 790
Balance as of end of period (4,373) (5,425) (4,373) (5,425)
Tax on amounts reclassified from accumulated other comprehensive loss (79) (79) (238) (238)
Postemployment Benefit Obligation        
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]        
Balance as of beginning of period (6,310) (697) (6,300) (306)
Amounts reclassified from accumulated other comprehensive loss, net of tax (7) (196) (17) (587)
Balance as of end of period (6,317) (893) (6,317) (893)
Tax on amounts reclassified from accumulated other comprehensive loss $ 1 $ 58 $ 4 $ 174