Lines of Business (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Lines of Business
External revenue	$ 409,465	$ 355,123
Intercompany revenue	0
Total revenue	409,465	355,123
Direct costs	316,086	275,345
Gross profit	93,379	79,778
Selling, general and administrative expense	39,051	26,183
Net (gain) loss on sale of assets	523	89
Operating income (loss)	53,805	53,506
Depreciation and amortization	16,562	13,380
Property and equipment additions	16,072	12,034
Total assets	2,129,591		1,995,368
Animal Hospital [Member]
Lines of Business
External revenue	316,125	269,941
Intercompany revenue	0
Total revenue	316,125	269,941
Direct costs	270,569	230,388
Gross profit	45,556	39,553
Selling, general and administrative expense	7,057	6,083
Net (gain) loss on sale of assets	505	78
Operating income (loss)	37,994	33,392
Depreciation and amortization	11,344	9,873
Property and equipment additions	10,766	9,535
Total assets	1,563,615		1,439,103
Laboratory [Member]
Lines of Business
External revenue	71,971	69,096
Intercompany revenue	12,759	10,453
Total revenue	84,730	79,549
Direct costs	44,179	42,819
Gross profit	40,551	36,730
Selling, general and administrative expense	7,598	6,636
Net (gain) loss on sale of assets	(7)	11
Operating income (loss)	32,960	30,083
Depreciation and amortization	2,553	2,471
Property and equipment additions	1,067	1,236
Total assets	243,220		232,423
All Other [Member]
Lines of Business
External revenue	21,369	16,086
Intercompany revenue	4,956	3,010
Total revenue	26,325	19,096
Direct costs	17,658	14,638
Gross profit	8,667	4,458
Selling, general and administrative expense	9,283	3,556
Net (gain) loss on sale of assets	8
Operating income (loss)	(624)	902
Depreciation and amortization	2,263	657
Property and equipment additions	1,722	759
Total assets	229,372		202,187
Corporate [Member]
Lines of Business
External revenue	0
Intercompany revenue	0
Total revenue	0
Direct costs	0
Gross profit	0
Selling, general and administrative expense	15,113	9,908
Net (gain) loss on sale of assets	17
Operating income (loss)	(15,130)	(9,908)
Depreciation and amortization	764	680
Property and equipment additions	2,983	958
Total assets	116,748		142,793
Intercompany Eliminations [Member]
Lines of Business
External revenue	0
Intercompany revenue	(17,715)	(13,463)
Total revenue	(17,715)	(13,463)
Direct costs	(16,320)	(12,500)
Gross profit	(1,395)	(963)
Selling, general and administrative expense	0
Net (gain) loss on sale of assets	0
Operating income (loss)	(1,395)	(963)
Depreciation and amortization	(362)	(301)
Property and equipment additions	(466)	(454)
Total assets	$ (23,364)		$ (21,138)