Summary of Significant Accounting Policies - Narrative (Details)		3 Months Ended	12 Months Ended
	Oct. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) province Hospital unit State shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($)
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of states in which management services are provided to animal hospitals | State			15
Number of Canadian Provinces in which entity operates | province			4
Impaired customer acquisition costs			$ 0	$ 0	$ 0
Depreciation and amortization expense			81,688,000	79,427,000	77,409,000
Accumulated depreciation on buildings and equipment held under capital leases			$ 387,466,000	352,212,000
Number of reporting units | unit			5
Impairment of goodwill and other long-lived assets	$ 0			0	9,246,000
Asset impairment charge				13,100,000
Likelihood of benefit amount being realized upon settlement in order to be recognized as a tax benefit			greater than 50%
Unrecognized Tax Benefit			We did not have any unrecognized tax benefits
Valuation allowances recorded			$ 21,775,000	19,846,000	17,702,000	$ 16,546,000
Accumulated amortization of deferred financing cost			1,700,000	1,400,000
Total marketing and advertising expense included in direct costs			25,500,000	23,900,000	25,400,000
Total marketing and advertising expenses included in selling, general and administrative expense			7,500,000	6,800,000	$ 5,900,000
Accrued warranty costs			$ 50,000	$ 0
Common shares excluded from the computation of diluted earnings per share | shares			55,351	31,668	43,300
Inventory adjustments					$ 2,800,000
Notes Receivable [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Valuation allowances recorded			$ 0	$ 0
Minimum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Interest rate on note receivable (percentage)			2.60%
Maximum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Interest rate on note receivable (percentage)			7.50%
Assets Held under Capital Leases [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Depreciation and amortization expense			$ 58,300,000	58,400,000	56,500,000
Accumulated depreciation on buildings and equipment held under capital leases			$ 19,100,000	$ 17,000,000
Other Segments [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Impairment of goodwill and other long-lived assets		$ 0			$ 9,246,000
United States
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of animal hospitals where management services are provided | Hospital			198
Canada
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of animal hospitals where management services are provided | Hospital			76