Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Revenues	$ 890,158	$ 768,415	$ 2,473,665	$ 2,108,592
Cost of services	650,561	573,634	1,847,172	1,598,394
Gross profit	239,597	194,781	626,493	510,198
Selling, general and administrative expenses	127,334	104,694	346,417	285,816
Contingent consideration	338	43	1,016	78
Loss (gain) on sale of assets	23	(132)	(156)	(1,576)
Operating income (loss)	111,902	90,176	279,216	225,880
Interest expense	534	395	1,318	1,198
Other (income) expense, net	2,617	570	(7,199)	313
Income (loss) from operations before income taxes	108,751	89,211	285,097	224,369
Provision for (benefit from) income taxes	29,464	22,572	75,537	57,342
Net income (loss)	79,287	66,639	209,560	167,027
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest	2,057	4,539	5,375	11,062
Net income attributable to noncontrolling interest			(5,375)	(11,062)
Net Income (Loss) Available to Common Stockholders, Basic	$ 77,230	$ 62,100	$ 204,185	$ 155,965
Earnings Per Share, Basic	$ 3.86	$ 2.71	$ 10.16	$ 6.92
Earnings Per Share, Diluted	$ 3.81	$ 2.67	$ 10.03	$ 6.84
Weighted Average Number of Shares Outstanding, Basic	19,856,289	20,224,102	19,938,694	20,216,981
Weighted Average Number of Shares Outstanding, Diluted	20,104,257	20,496,870	20,188,035	20,462,856