Lines of Business (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Lines of Business
External revenue	$ 465,255	$ 438,372	$ 903,861	$ 847,837
Intercompany revenue	0	0	0	0
Total revenue	465,255	438,372	903,861	847,837
Direct costs	350,961	337,765	692,644	653,851
Gross profit	114,294	100,607	211,217	193,986
Selling, general and administrative expense	39,023	38,997	78,869	78,048
operating income before significant charges	75,271	61,610	132,348	115,938
Net (gain) loss on sale of assets	(430)	112	1,296	635
Operating income (loss)	75,701	61,498	131,052	115,303
Depreciation and amortization	19,500	20,801	37,739	37,363
Property and equipment additions	15,126	21,093	33,095	37,165
Total assets	2,175,499		2,175,499		2,091,580
Animal Hospital [Member]
Lines of Business
External revenue	365,205	342,282	705,820	658,407
Intercompany revenue	0	0	0	0
Total revenue	365,205	342,282	705,820	658,407
Direct costs	305,092	292,902	600,508	563,471
Gross profit	60,113	49,380	105,312	94,936
Selling, general and administrative expense	8,720	7,995	17,045	15,052
operating income before significant charges	51,393	41,385	88,267	79,884
Net (gain) loss on sale of assets	(160)	(112)	1,569	393
Operating income (loss)	51,553	41,497	86,698	79,491
Depreciation and amortization	14,684	15,239	28,071	26,583
Property and equipment additions	11,326	15,297	25,767	26,063
Total assets	1,802,057		1,802,057		1,648,578
Laboratory [Member]
Lines of Business
External revenue	77,937	72,452	151,576	144,423
Intercompany revenue	13,293	14,168	26,989	26,927
Total revenue	91,230	86,620	178,565	171,350
Direct costs	46,004	44,324	90,874	88,503
Gross profit	45,226	42,296	87,691	82,847
Selling, general and administrative expense	7,965	7,510	15,970	15,108
operating income before significant charges	37,261	34,786	71,721	67,739
Net (gain) loss on sale of assets	(1)	(7)	(6)	(14)
Operating income (loss)	37,262	34,793	71,727	67,753
Depreciation and amortization	2,590	2,521	5,097	5,074
Property and equipment additions	1,818	2,282	3,736	3,349
Total assets	252,070		252,070		244,551
All Other [Member]
Lines of Business
External revenue	22,113	23,638	46,465	45,007
Intercompany revenue	5,359	3,780	9,530	8,736
Total revenue	27,472	27,418	55,995	53,743
Direct costs	18,049	17,624	36,938	35,282
Gross profit	9,423	9,794	19,057	18,461
Selling, general and administrative expense	8,041	9,029	16,955	18,312
operating income before significant charges	1,382	765	2,102	149
Net (gain) loss on sale of assets	1	232	3	240
Operating income (loss)	1,381	533	2,099	(91)
Depreciation and amortization	1,937	2,582	3,902	4,845
Property and equipment additions	1,039	1,048	2,372	2,770
Total assets	96,938		96,938		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	14,297	14,463	28,899	29,576
operating income before significant charges	(14,297)	(14,463)	(28,899)	(29,576)
Net (gain) loss on sale of assets	(270)	(1)	(270)	16
Operating income (loss)	(14,027)	(14,462)	(28,629)	(29,592)
Depreciation and amortization	735	804	1,554	1,568
Property and equipment additions	1,306	3,008	1,946	5,991
Total assets	54,368		54,368		127,963
Intercompany Eliminations [Member]
Lines of Business
External revenue	0	0	0	0
Intercompany revenue	(18,652)	(17,948)	(36,519)	(35,663)
Total revenue	(18,652)	(17,948)	(36,519)	(35,663)
Direct costs	(18,184)	(17,085)	(35,676)	(33,405)
Gross profit	(468)	(863)	(843)	(2,258)
Selling, general and administrative expense	0	0	0	0
operating income before significant charges	(468)	(863)	(843)	(2,258)
Net (gain) loss on sale of assets	0	0	0	0
Operating income (loss)	(468)	(863)	(843)	(2,258)
Depreciation and amortization	(446)	(345)	(885)	(707)
Property and equipment additions	(363)	(542)	(726)	(1,008)
Total assets	$ (29,934)		$ (29,934)		$ (27,671)