Lines of Business (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Lines of Business
External revenue	$ 385,135	$ 358,703	$ 1,116,363	$ 1,043,356
Total revenue	385,135	358,703	1,116,363	1,043,356
Direct costs	294,998	273,404	849,616	781,778
Gross profit	90,137	85,299	266,747	261,578
Selling, general and administrative expense	32,488	27,105	85,334	94,290
Net (gain) loss on sale of assets	(192)	152	(43)	163
Operating income (loss)	57,841	58,042	181,456	167,125
Depreciation and amortization	14,930	11,681	41,386	33,387
Property and equipment additions	14,841	19,750	43,275	47,675
Total assets	1,996,814		1,996,814		1,766,422
Animal Hospital [Member]
Lines of Business
External revenue	303,203	276,739	864,476	791,002
Total revenue	303,203	276,739	864,476	791,002
Direct costs	251,613	230,113	720,393	653,671
Gross profit	51,590	46,626	144,083	137,331
Selling, general and administrative expense	6,126	5,599	18,253	16,859
Net (gain) loss on sale of assets	(213)	114	(84)	63
Operating income (loss)	45,677	40,913	125,914	120,409
Depreciation and amortization	10,393	8,258	29,799	23,240
Property and equipment additions	11,061	16,969	33,832	39,946
Total assets	1,417,062		1,417,062		1,320,619
Laboratory [Member]
Lines of Business
External revenue	67,588	67,872	209,639	210,531
Intercompany revenue	11,397	9,420	33,280	27,913
Total revenue	78,985	77,292	242,919	238,444
Direct costs	43,657	42,579	130,192	126,647
Gross profit	35,328	34,713	112,727	111,797
Selling, general and administrative expense	7,088	6,804	20,577	19,485
Net (gain) loss on sale of assets	1	20	19	21
Operating income (loss)	28,239	27,889	92,131	92,291
Depreciation and amortization	2,563	2,464	7,542	7,273
Property and equipment additions	1,085	1,599	4,049	3,937
Total assets	229,252		229,252		215,483
All Other [Member]
Lines of Business
External revenue	14,344	14,092	42,248	41,823
Intercompany revenue	4,538	3,314	11,939	5,982
Total revenue	18,882	17,406	54,187	47,805
Direct costs	14,149	12,152	40,206	33,373
Gross profit	4,733	5,254	13,981	14,432
Selling, general and administrative expense	4,669	3,731	11,809	10,650
Net (gain) loss on sale of assets	20	17	22	71
Operating income (loss)	44	1,506	2,150	3,711
Depreciation and amortization	1,606	606	2,931	1,812
Property and equipment additions	1,986	428	3,003	634
Total assets	220,964		220,964		69,082
Corporate [Member]
Lines of Business
Selling, general and administrative expense	14,605	10,971	34,695	47,296
Net (gain) loss on sale of assets		1		8
Operating income (loss)	(14,605)	(10,972)	(34,695)	(47,304)
Depreciation and amortization	702	616	2,067	1,815
Property and equipment additions	1,338	1,394	3,923	4,579
Total assets	149,801		149,801		175,297
Intercompany Eliminations [Member]
Lines of Business
Intercompany revenue	(15,935)	(12,734)	(45,219)	(33,895)
Total revenue	(15,935)	(12,734)	(45,219)	(33,895)
Direct costs	(14,421)	(11,440)	(41,175)	(31,913)
Gross profit	(1,514)	(1,294)	(4,044)	(1,982)
Operating income (loss)	(1,514)	(1,294)	(4,044)	(1,982)
Depreciation and amortization	(334)	(263)	(953)	(753)
Property and equipment additions	(629)	(640)	(1,532)	(1,421)
Total assets	$ (20,265)		$ (20,265)		$ (14,059)