Consolidated Statement Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Consolidated Statement Of Income [Abstract]
Service revenues and sales	$ 352,943	$ 330,918
Cost of services provided and goods sold (excluding depreciation)	257,445	237,458
Selling, general and administrative expenses	53,167	55,654
Depreciation	6,241	6,288
Amortization	1,113	970
Total costs and expenses	317,966	300,370
Income from operations	34,977	30,548
Interest expense	(3,617)	(3,244)
Other income - net	2,095	2,102
Income before income taxes	33,455	29,406
Income taxes	(13,010)	(11,305)
Net income	$ 20,445	$ 18,101
Earnings Per Share
Net income	$ 1.08	$ 0.86
Average number of shares outstanding	18,958	21,055
Diluted Earnings Per Share
Net income	$ 1.06	$ 0.84
Average number of shares outstanding	19,353	21,568
Cash Dividends Per Share	$ 0.16	$ 0.14