Goodwill and Other Long-Lived Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Goodwill [Line Items]
Goodwill	$ 1,569,655		$ 1,545,918
Accumulated impairment losses	(130,057)		(130,057)
Subtotal	1,439,598		1,415,861
Goodwill acquired	34,818
Foreign translation adjustment	(11,028)
Other	(53)	[1]
Animal Hospital [Member]
Goodwill [Line Items]
Goodwill	1,308,091		1,305,558
Accumulated impairment losses	0		0
Subtotal	1,308,091		1,305,558
Goodwill acquired	13,563
Foreign translation adjustment	(10,981)
Other	(49)	[1]
Laboratory [Member]
Goodwill [Line Items]
Goodwill	118,484		97,535
Accumulated impairment losses	0		0
Subtotal	118,484		97,535
Goodwill acquired	21,000
Foreign translation adjustment	(47)
Other	(4)	[1]
All Other [Member]
Goodwill [Line Items]
Goodwill	143,080		142,825
Accumulated impairment losses	(130,057)		(130,057)
Subtotal	13,023		12,768
Goodwill acquired	255
Foreign translation adjustment	0
Other	$ 0	[1]

[1] "Other" primarily includes measurement period adjustments, a partnership buyout and a write-off related to the sale of an animal hospital.