Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Consolidated Statements Of Income [Abstract]
Service revenues and sales	$ 618,798	$ 595,880	$ 1,265,741	$ 1,185,113
Cost of services provided and goods sold (excluding depreciation)	434,105	389,750	864,635	774,877
Selling, general and administrative expenses	100,323	102,255	205,910	218,128
Depreciation	13,689	13,167	27,134	26,454
Amortization	2,571	2,546	5,143	5,067
Other operating expense	26	37	77	129
Total costs and expenses	550,714	507,755	1,102,899	1,024,655
Income from operations	68,084	88,125	162,842	160,458
Interest expense	(443)	(429)	(772)	(854)
Other income - net	3,474	6,132	4,719	18,709
Income before income taxes	71,115	93,828	166,789	178,313
Income taxes	(18,622)	(22,941)	(42,539)	(42,409)
Net income	$ 52,493	$ 70,887	$ 124,250	$ 135,904
Earnings Per Share:
Net income	$ 3.60	$ 4.70	$ 8.51	$ 8.99
Average number of shares outstanding	14,591	15,097	14,606	15,109
Diluted Earnings Per Share:
Net income	$ 3.57	$ 4.65	$ 8.43	$ 8.89
Average number of shares outstanding	14,703	15,251	14,733	15,295
Cash Dividends Per Share	$ 0.50	$ 0.40	$ 1.00	$ 0.80