Acquisitions (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ (52,688)	$ (134,916)	$ (205,794)
Consideration:
Cash paid to holders of debt	2,360	0	0
Business Combination, Contingent Consideration, Liability	(2,200)	(1,500)
Goodwill, Acquired During Period	45,665	156,115
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	57,425	82,360	35,822
Noncontrolling Interest, Increase from Business Combination	(3,336)	8,161	0
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value	0	(11,850)	0
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	(52,688)	(78,629)	(34,243)
Consideration:
Cash paid for holdbacks	1,092	2,425	1,500
Business Combination, Contingent Consideration, Liability	1,285	1,306	79
Fair value of total consideration transferred	57,425	82,360	35,822
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	14,779	3,515	1,237
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	15,001	14,718	6,414
Goodwill, Acquired During Period	45,665	64,253	28,171
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	(11,084)	(126)	0
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	64,361	82,360	35,822
Noncontrolling Interest, Increase from Business Combination	(6,936)	0	0
Think Pets Inc [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired		(7,468)
Consideration:
Cash paid for holdbacks		1,050
Fair value of total consideration transferred		19,018
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		2,093
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		7,221
Goodwill, Acquired During Period		12,155
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		(2,451)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net		19,018
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned		(10,500)
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	8 years
Animal Hospitals and Laboratory Acquisitions [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired		(48,819)
Consideration:
Cash paid to holders of debt		25,915
Fair value of total consideration transferred		74,734
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		11,694
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		25,170
Goodwill, Acquired During Period		79,707
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		(21,826)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net		74,734
business acquisition purchase price allocation total		94,745
Noncontrolling Interest, Increase from Business Combination		8,161
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value		$ (11,850)
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years
Customer Relationships [Member] | Think Pets Inc [Member]
Consideration:
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years
Customer Relationships [Member] | Animal Hospitals and Laboratory Acquisitions [Member]
Consideration:
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years