Summary of Significant Accounting Policies - Narrative (Details)		12 Months Ended
	Oct. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) province unit State Hospital shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of states in which management services are provided to animal hospitals | State		16
Number of Canadian Provinces in which entity operates | province		5
Impaired customer acquisition costs		$ 0	$ 0	$ 0
Depreciation and amortization expense		102,942,000	81,688,000	79,427,000
Accumulated depreciation on buildings and equipment held under capital leases		$ 439,360,000	387,466,000
Number of reporting units | unit		5
Impairment of goodwill and other long-lived assets	$ 0
Unrecognized tax benefits		$ 0	0
Valuation allowances recorded		23,440,000	21,775,000	19,846,000	$ 17,702,000
Accumulated amortization of deferred financing cost		1,700,000	1,700,000
Total marketing and advertising expense included in direct costs		26,200,000	25,500,000	23,900,000
Total marketing and advertising expenses included in selling, general and administrative expense		7,900,000	7,500,000	$ 6,800,000
Accrued warranty costs		$ 50,000	$ 50,000
Common shares excluded from the computation of diluted earnings per share (in shares) | shares		15,481	55,351	31,668
Notes Receivable
Summary of Significant Accounting Policies (Textual) [Abstract]
Valuation allowances recorded		$ 0	$ 0
Minimum
Summary of Significant Accounting Policies (Textual) [Abstract]
Interest rate on note receivable (percentage)		2.60%
Maximum
Summary of Significant Accounting Policies (Textual) [Abstract]
Interest rate on note receivable (percentage)		7.50%
Assets Held under Capital Leases
Summary of Significant Accounting Policies (Textual) [Abstract]
Depreciation and amortization expense		$ 65,200,000	58,300,000	$ 58,400,000
Accumulated depreciation on buildings and equipment held under capital leases		$ 20,900,000	$ 19,100,000
United States
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of animal hospitals where management services are provided | Hospital		228
Canada
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of animal hospitals where management services are provided | Hospital		86