Consolidated Statement Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Consolidated Statement Of Income [Abstract]
Service revenues and sales	$ 390,389	$ 376,652
Cost of services provided and goods sold (excluding depreciation)	278,435	268,885
Selling, general and administrative expenses	59,045	59,037
Depreciation	8,424	8,032
Amortization	92	127
Total costs and expenses	345,996	336,081
Income from operations	44,393	40,571
Interest expense	(842)	(969)
Other income/(expense) - net	(2,924)	563
Income before income taxes	40,627	40,165
Income taxes	(15,787)	(15,628)
Net income	$ 24,840	$ 24,537
Earnings Per Share
Net income	$ 1.49	$ 1.45
Average number of shares outstanding	16,720	16,914
Diluted Earnings Per Share
Net income	$ 1.45	$ 1.40
Average number of shares outstanding	17,170	17,466
Cash Dividends Per Share	$ 0.24	$ 0.22