CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2014	$ 53,132	$ 63	$ 222,297	$ 283	$ (169,511)
Beginning balance (in shares) at Dec. 31, 2014		6,342
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,519				5,519
Issuance of common stock, net of shares withheld for employee taxes	1,258	$ 3	1,255
Issuance of common stock related to options, ESPP and other (in shares)		283
Stock-based compensation	2,269		2,269
Excess tax benefit from stock-based compensation	1,514		1,514
Accretion of non-controlling interest	(68)		(68)
Other comprehensive income (loss)	(96)			(96)
Ending balance at Dec. 31, 2015	63,528	$ 66	227,267	187	(163,992)
Ending balance (in shares) at Dec. 31, 2015		6,625
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,165				12,165
Issuance of common stock, net of shares withheld for employee taxes	1,618	$ 2	1,616
Issuance of common stock related to options, ESPP and other (in shares)		226
Issuance of common stock related to the acquisition of Cuattro Veterinary International, LLC	6,349	$ 2	6,347
Issuance of common stock related to the acquisition of Cuattro Veterinary International, LLC (in shares)		175
Stock-based compensation	2,260		2,260
Accretion of non-controlling interest	1,145		1,145
Other comprehensive income (loss)	(90)			(90)
Ending balance at Dec. 31, 2016	86,975	$ 70	238,635	97	(151,827)
Ending balance (in shares) at Dec. 31, 2016		7,026
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9,456				9,456
Issuance of common stock, net of shares withheld for employee taxes	1,376	$ 3	1,373
Issuance of common stock related to options, ESPP and other (in shares)		277
Stock-based compensation	2,745		2,745
Accretion of non-controlling interest	845		845
Dividends	(1,092)				(1,092)
Other comprehensive income (loss)	135			135
Ending balance at Dec. 31, 2017	$ 100,440	$ 73	$ 243,598	$ 232	$ (143,463)
Ending balance (in shares) at Dec. 31, 2017		7,303