Lines of Business (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Lines of Business
External revenue	$ 438,606	$ 409,465
Intercompany revenue	0	0
Total revenue	438,606	409,465
Direct costs	341,683	316,086
Gross profit	96,923	93,379
Selling, general and administrative expense	39,846	39,051
operating income before significant charges	57,077	54,328
Net (gain) loss on sale of assets	1,726	523
Operating income (loss)	55,351	53,805
Depreciation and amortization	18,239	16,562
Property and equipment additions	17,969	16,072
Total assets	2,137,702		2,091,580
Animal Hospital [Member]
Lines of Business
External revenue	340,615	316,125
Intercompany revenue	0	0
Total revenue	340,615	316,125
Direct costs	295,416	270,569
Gross profit	45,199	45,556
Selling, general and administrative expense	8,325	7,057
operating income before significant charges	36,874	38,499
Net (gain) loss on sale of assets	1,729	505
Operating income (loss)	35,145	37,994
Depreciation and amortization	13,387	11,344
Property and equipment additions	14,441	10,766
Total assets	1,762,143		1,648,578
Laboratory [Member]
Lines of Business
External revenue	73,638	71,971
Intercompany revenue	13,697	12,759
Total revenue	87,335	84,730
Direct costs	44,870	44,179
Gross profit	42,465	40,551
Selling, general and administrative expense	8,005	7,598
operating income before significant charges	34,460	32,953
Net (gain) loss on sale of assets	(5)	(7)
Operating income (loss)	34,465	32,960
Depreciation and amortization	2,507	2,553
Property and equipment additions	1,918	1,067
Total assets	255,689		244,551
All Other [Member]
Lines of Business
External revenue	24,353	21,369
Intercompany revenue	4,170	4,956
Total revenue	28,523	26,325
Direct costs	18,889	17,658
Gross profit	9,634	8,667
Selling, general and administrative expense	8,914	9,283
operating income before significant charges	720	(616)
Net (gain) loss on sale of assets	2	8
Operating income (loss)	718	(624)
Depreciation and amortization	1,965	2,263
Property and equipment additions	1,333	1,722
Total assets	97,095		98,159
Corporate [Member]
Lines of Business
External revenue	0	0
Intercompany revenue	0	0
Total revenue	0	0
Direct costs	0	0
Gross profit	0	0
Selling, general and administrative expense	14,602	15,113
operating income before significant charges	(14,602)	(15,113)
Net (gain) loss on sale of assets	0	17
Operating income (loss)	(14,602)	(15,130)
Depreciation and amortization	819	764
Property and equipment additions	640	2,983
Total assets	55,959		127,963
Intercompany Eliminations [Member]
Lines of Business
External revenue	0	0
Intercompany revenue	(17,867)	(17,715)
Total revenue	(17,867)	(17,715)
Direct costs	(17,492)	(16,320)
Gross profit	(375)	(1,395)
Selling, general and administrative expense	0	0
operating income before significant charges	(375)	(1,395)
Net (gain) loss on sale of assets	0	0
Operating income (loss)	(375)	(1,395)
Depreciation and amortization	(439)	(362)
Property and equipment additions	(363)	(466)
Total assets	$ (33,184)		$ (27,671)