Lines of Business (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
External revenue									$ 1,699,642	$ 1,485,361	$ 1,381,468
Revenue, Net	418,192	433,613	438,372	409,465	368,998	385,135	376,105	355,123	1,699,642	1,485,361	1,381,468
Intercompany revenue									0	0	0
Capital expenditures									76,807	63,485	61,951
Gross Profit	81,807	99,181	100,607	93,379	71,710	90,137	96,832	79,778	374,974	338,457	331,164
Direct costs									1,324,668	1,146,904	1,050,304
Selling, General and Administrative Expense									157,155	121,112	123,541
Operating income before significant charges									217,819	217,345
Asset Impairment Charges									123,573
Goodwill impairment									99,501	21,310	0
Gain (Loss) on Disposition of Assets									1,310	382	374
Disclosure on Geographic Areas, Description of Revenue from External Customers									*Revenues are determined based on the location of the customer.
Operating income (loss)	(83,553)	61,186	61,498	53,805	14,197	57,841	70,109	53,506	92,936	195,653	207,249
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Entity's Country of Domicile									1,589,588	1,474,294	1,374,835
Assets	2,091,580				1,995,368				2,091,580	1,995,368	1,766,422
Depreciation and amortization									76,227	56,988	46,069
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries									110,054	11,067	6,633
Animal Hospital [Member]
Segment Reporting Information [Line Items]
External revenue									1,331,314	1,150,120	1,052,462
Revenue, Net									1,331,314	1,150,120	1,052,462
Intercompany revenue									0	0	0
Capital expenditures									55,651	45,753	52,243
Gross Profit									189,111	179,810	172,390
Direct costs									1,142,203	970,310	880,072
Selling, General and Administrative Expense									30,826	24,342	23,539
Operating income before significant charges									158,285	155,468
Asset Impairment Charges									1,216
Goodwill impairment									0	0
Gain (Loss) on Disposition of Assets									713	327	273
Operating income (loss)									156,356	155,141	148,578
Assets	1,648,578				1,439,103				1,648,578	1,439,103	1,320,619
Depreciation and amortization									54,835	40,319	32,456
Laboratory [Member]
Segment Reporting Information [Line Items]
External revenue									275,406	272,468	273,616
Revenue, Net									327,801	316,797	310,654
Intercompany revenue									52,395	44,329	37,038
Capital expenditures									8,334	6,082	5,176
Gross Profit									151,761	143,790	142,196
Direct costs									176,040	173,007	168,458
Selling, General and Administrative Expense									29,660	27,864	26,243
Operating income before significant charges									122,101	115,926
Asset Impairment Charges									0
Goodwill impairment									0	0
Gain (Loss) on Disposition of Assets									(14)	21	(22)
Operating income (loss)									122,115	115,905	115,931
Assets	244,551				232,423				244,551	232,423	215,483
Depreciation and amortization									10,141	10,111	9,738
Other Segments [Member]
Segment Reporting Information [Line Items]
External revenue									92,922	62,773	55,390
Revenue, Net									112,960	80,430	64,013
Intercompany revenue									20,038	17,657	8,623
Capital expenditures									5,921	6,448	857
Gross Profit									38,707	20,971	19,277
Direct costs									74,253	59,459	44,736
Selling, General and Administrative Expense									37,879	19,136	14,507
Operating income before significant charges									828	1,835
Asset Impairment Charges									122,357
Goodwill impairment									99,501	21,310
Gain (Loss) on Disposition of Assets									717	27	71
Operating income (loss)									(122,246)	(19,502)	4,699
Assets	98,159				202,187				98,159	202,187	69,082
Depreciation and amortization									9,582	5,022	2,437
Corporate [Member]
Segment Reporting Information [Line Items]
External revenue									0	0	0
Revenue, Net									0	0	0
Intercompany revenue									0	0	0
Capital expenditures									9,695	7,299	5,516
Gross Profit									0	0	0
Direct costs									0	0	0
Selling, General and Administrative Expense									58,790	49,770	59,252
Operating income before significant charges									(58,790)	(49,770)
Asset Impairment Charges									0
Goodwill impairment										0
Gain (Loss) on Disposition of Assets									(106)	7	8
Operating income (loss)									(58,684)	(49,777)	(59,260)
Assets	127,963				142,793				127,963	142,793	175,297
Depreciation and amortization									3,198	2,853	2,474
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
External revenue									0	0	0
Revenue, Net									(72,433)	(61,986)	(45,661)
Intercompany revenue									(72,433)	(61,986)	(45,661)
Capital expenditures									(2,794)	(2,097)	(1,841)
Gross Profit									(4,605)	(6,114)	(2,699)
Direct costs									(67,828)	(55,872)	(42,962)
Selling, General and Administrative Expense									0	0	0
Operating income before significant charges									(4,605)	(6,114)
Asset Impairment Charges									0
Goodwill impairment										0
Gain (Loss) on Disposition of Assets									0	0	0
Operating income (loss)									(4,605)	(6,114)	(2,699)
Assets	(27,671)				(21,138)				(27,671)	(21,138)	(14,059)
Depreciation and amortization									$ (1,529)	$ (1,317)	$ (1,036)