Lines of Business (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Lines of Business
External revenue	$ 464,055	$ 433,613	$ 1,367,916	$ 1,281,450
Intercompany revenue	0	0	0	0
Total revenue	464,055	433,613	1,367,916	1,281,450
Direct costs	353,378	334,432	1,046,022	988,283
Gross profit	110,677	99,181	321,894	293,167
Selling, general and administrative expense	38,747	37,608	117,616	115,656
operating income before significant charges	71,930	61,573	204,278	177,511
Net (gain) loss on sale of assets	(109)	387	1,187	1,022
Operating income (loss)	72,039	61,186	203,091	176,489
Depreciation and amortization	20,044	19,519	57,783	56,882
Property and equipment additions	19,587	18,092	52,682	55,257
Total assets	2,235,335		2,235,335		2,091,580
Animal Hospital [Member]
Lines of Business
External revenue	368,868	342,840	1,074,688	1,001,247
Intercompany revenue	0	0	0	0
Total revenue	368,868	342,840	1,074,688	1,001,247
Direct costs	308,029	288,588	908,537	852,059
Gross profit	60,839	54,252	166,151	149,188
Selling, general and administrative expense	8,678	7,745	25,723	22,797
operating income before significant charges	52,161	46,507	140,428	126,391
Net (gain) loss on sale of assets	(110)	(77)	1,459	316
Operating income (loss)	52,271	46,584	138,969	126,075
Depreciation and amortization	15,037	13,953	43,108	40,536
Property and equipment additions	15,915	14,069	41,682	40,132
Total assets	1,849,587		1,849,587		1,648,578
Laboratory [Member]
Lines of Business
External revenue	72,877	68,139	223,466	212,562
Intercompany revenue	13,583	13,147	41,559	40,074
Total revenue	86,460	81,286	265,025	252,636
Direct costs	45,650	44,109	136,524	132,612
Gross profit	40,810	37,177	128,501	120,024
Selling, general and administrative expense	7,921	7,285	23,891	22,393
operating income before significant charges	32,889	29,892	104,610	97,631
Net (gain) loss on sale of assets	11	0	5	(14)
Operating income (loss)	32,878	29,892	104,605	97,645
Depreciation and amortization	2,554	2,544	7,651	7,618
Property and equipment additions	1,905	1,342	5,641	4,691
Total assets	252,179		252,179		244,551
All Other [Member]
Lines of Business
External revenue	21,482	21,970	67,339	65,926
Intercompany revenue	5,980	6,130	16,118	15,917
Total revenue	27,462	28,100	83,457	81,843
Direct costs	17,456	19,217	54,394	54,499
Gross profit	10,006	8,883	29,063	27,344
Selling, general and administrative expense	7,618	8,764	24,573	27,076
operating income before significant charges	2,388	119	4,490	268
Net (gain) loss on sale of assets	0	464	3	704
Operating income (loss)	2,388	(345)	4,487	(436)
Depreciation and amortization	2,087	2,611	5,989	7,456
Property and equipment additions	872	1,660	3,244	4,430
Total assets	99,435		99,435		98,159
Corporate [Member]
Lines of Business
External revenue	0	0	0	0
Intercompany revenue	0	0	0	0
Total revenue	0	0	0	0
Direct costs	0	0	0	0
Gross profit	0	0	0	0
Selling, general and administrative expense	14,530	13,814	43,429	43,390
operating income before significant charges	(14,530)	(13,814)	(43,429)	(43,390)
Net (gain) loss on sale of assets	(10)	0	(280)	16
Operating income (loss)	(14,520)	(13,814)	(43,149)	(43,406)
Depreciation and amortization	816	806	2,370	2,374
Property and equipment additions	1,795	2,120	3,741	8,111
Total assets	63,803		63,803		127,963
Intercompany Eliminations [Member]
Lines of Business
External revenue	828	664	2,423	1,715
Intercompany revenue	(19,563)	(19,277)	(57,677)	(55,991)
Total revenue	(18,735)	(18,613)	(55,254)	(54,276)
Direct costs	(17,757)	(17,482)	(53,433)	(50,887)
Gross profit	(978)	(1,131)	(1,821)	(3,389)
Selling, general and administrative expense	0	0	0	0
operating income before significant charges	(978)	(1,131)	(1,821)	(3,389)
Net (gain) loss on sale of assets	0	0	0	0
Operating income (loss)	(978)	(1,131)	(1,821)	(3,389)
Depreciation and amortization	(450)	(395)	(1,335)	(1,102)
Property and equipment additions	(900)	(1,099)	(1,626)	(2,107)
Total assets	$ (29,669)		$ (29,669)		$ (27,671)