Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Consolidated Statements Of Income [Abstract]
Service revenues and sales	$ 515,798	$ 462,034
Cost of services provided and goods sold (excluding depreciation)	351,745	321,951
Selling, general and administrative expenses	70,583	74,029
Depreciation	11,388	9,710
Amortization	2,477	519
Other operating expenses	242	6,353
Total costs and expenses	436,435	412,562
Income from operations	79,363	49,472
Interest expense	(975)	(1,124)
Other (expense)/income - net	(9,466)	2,439
Income before income taxes	68,922	50,787
Income taxes	(13,031)	(6,120)
Net income	$ 55,891	$ 44,667
Earnings Per Share:
Net income	$ 3.50	$ 2.80
Average number of shares outstanding	15,991	15,954
Diluted Earnings Per Share:
Net income	$ 3.38	$ 2.70
Average number of shares outstanding	16,516	16,525
Cash Dividends Per Share	$ 0.32	$ 0.30