Goodwill and Other Long-Lived Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill	$ 1,498,287	$ 1,451,728
Accumulated impairment losses	(130,057)	(120,811)
Subtotal	1,368,230	1,330,917
Goodwill acquired		53,171
Goodwill impairment	(9,200)	(9,246)
Foreign translation adjustment		(5,204)
Other		(1,408)	[1]
Animal Hospital [Member]
Goodwill [Line Items]
Goodwill	1,256,472	1,216,581
Accumulated impairment losses	0	0
Subtotal	1,256,472	1,216,581
Goodwill acquired		46,475
Goodwill impairment		0
Foreign translation adjustment		(5,176)
Other		(1,408)	[1]
Laboratory [Member]
Goodwill [Line Items]
Goodwill	96,870	96,871
Accumulated impairment losses	0	0
Subtotal	96,870	96,871
Goodwill acquired		27
Goodwill impairment		0
Foreign translation adjustment		(28)
Other		0	[1]
All Other Segments [Member]
Goodwill [Line Items]
Goodwill	144,945	138,276
Accumulated impairment losses	(130,057)	(120,811)
Subtotal	14,888	17,465
Goodwill acquired		6,669
Goodwill impairment		(9,246)
Foreign translation adjustment		0
Other		$ 0	[1]

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