Lines of Business (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Lines of Business
External revenue									$ 1,485,361	$ 1,381,468	$ 1,314,507
Total revenue	368,998	385,135	376,105	355,123	338,112	358,703	353,919	330,734	1,485,361	1,381,468	1,314,507
Direct costs									1,146,904	1,050,304	973,275
Gross profit	71,710	90,137	96,832	79,778	69,586	85,299	93,484	82,795	338,457	331,164	341,232
Selling, general and administrative expense									121,112	123,541	95,669
Goodwill impairment									21,310
Net loss on sale of assets									382	374	4,035
Operating income (loss)	14,197	57,841	70,109	53,506	40,124	58,042	52,453	56,630	195,653	207,249	241,528
Depreciation and amortization									56,988	46,069	39,571
Capital expenditures									63,485	61,951	50,801
Total assets	1,995,368				1,766,422				1,995,368	1,766,422	1,627,404
Animal Hospital [Member]
Lines of Business
External revenue									1,150,120	1,052,462	994,215
Total revenue									1,150,120	1,052,462	994,215
Direct costs									970,310	880,072	810,517
Gross profit									179,810	172,390	183,698
Selling, general and administrative expense									24,342	23,539	21,174
Net loss on sale of assets									327	273	652
Operating income (loss)									155,141	148,578	161,872
Depreciation and amortization									40,319	32,456	26,769
Capital expenditures									45,753	52,243	40,137
Total assets	1,439,103				1,320,619				1,439,103	1,320,619	1,158,891
Laboratory [Member]
Lines of Business
External revenue									272,468	273,616	277,528
Intercompany revenue									44,329	37,038	32,529
Total revenue									316,797	310,654	310,057
Direct costs									173,007	168,458	166,565
Gross profit									143,790	142,196	143,492
Selling, general and administrative expense									27,864	26,243	22,895
Net loss on sale of assets									21	22	11
Operating income (loss)									115,905	115,931	120,586
Depreciation and amortization									10,111	9,738	9,325
Capital expenditures									6,082	5,176	7,518
Total assets	232,423				215,483				232,423	215,483	207,043
All Other [Member]
Lines of Business
External revenue									62,773	55,390	42,764
Intercompany revenue									17,657	8,623	5,793
Total revenue									80,430	64,013	48,557
Direct costs									59,459	44,736	32,721
Gross profit									20,971	19,277	15,836
Selling, general and administrative expense									19,136	14,507	12,885
Goodwill impairment									21,310
Net loss on sale of assets									27	71	11
Operating income (loss)									(19,502)	4,699	2,940
Depreciation and amortization									5,022	2,437	2,000
Capital expenditures									6,448	857	919
Total assets	202,187				69,082				202,187	69,082	71,019
Corporate [Member]
Lines of Business
Selling, general and administrative expense									49,770	59,252	38,715
Net loss on sale of assets									7	8	3,361
Operating income (loss)									(49,777)	(59,260)	(42,076)
Depreciation and amortization									2,853	2,474	2,307
Capital expenditures									7,299	5,516	3,994
Total assets	142,793				175,297				142,793	175,297	201,024
Intercompany Eliminations [Member]
Lines of Business
Intercompany revenue									(61,986)	(45,661)	(38,322)
Total revenue									(61,986)	(45,661)	(38,322)
Direct costs									(55,872)	(42,962)	(36,528)
Gross profit									(6,114)	(2,699)	(1,794)
Operating income (loss)									(6,114)	(2,699)	(1,794)
Depreciation and amortization									(1,317)	(1,036)	(830)
Capital expenditures									(2,097)	(1,841)	(1,767)
Total assets	$ (21,138)				$ (14,059)				$ (21,138)	$ (14,059)	$ (10,573)