Consolidated Statements Of Income Unaudited - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Consolidated Statements Of Income [Abstract]
Service revenues and sales	$ 531,288	$ 532,256	$ 1,061,837	$ 1,059,616
Cost of services provided and goods sold (excluding depreciation)	336,821	350,493	673,373	690,966
Selling, general and administrative expenses	87,853	93,838	177,807	185,437
Depreciation	12,714	13,612	24,852	25,327
Amortization	2,520	2,510	5,038	5,020
Other operating (income)/expense	(558)	104	(545)	726
Total costs and expenses	439,350	460,557	880,525	907,476
Income from operations	91,938	71,699	181,312	152,140
Interest expense	(902)	(379)	(1,712)	(760)
Other (expense)/income - net	(4,930)	3,785	(8,792)	7,387
Income before income taxes	86,106	75,105	170,808	158,767
Income taxes	(19,650)	(18,583)	(40,183)	(36,845)
Net income	$ 66,456	$ 56,522	$ 130,625	$ 121,922
Earnings Per Share:
Net income	$ 4.45	$ 3.57	$ 8.73	$ 7.66
Average number of shares outstanding	14,932	15,829	14,959	15,919
Diluted Earnings Per Share:
Net income	$ 4.40	$ 3.51	$ 8.62	$ 7.52
Average number of shares outstanding	15,111	16,101	15,152	16,205
Cash Dividends Per Share	$ 0.36	$ 0.34	$ 0.72	$ 0.68