CAPITAL STOCK - NARRATIVE (Details) $ / shares in Units, $ in Thousands					1 Months Ended				12 Months Ended
	Apr. 16, 2020 $ / shares shares	Apr. 14, 2020 shares	Apr. 01, 2020 USD ($)	Mar. 30, 2020 USD ($) $ / shares shares	Apr. 30, 2020 shares	May 31, 2018 shares	May 31, 2016 shares	May 31, 2012 shares	Dec. 31, 2020 USD ($) plans $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	May 31, 2003 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock option plans | plans									2
Expected dividend rate (as a percent)									0.00%	0.00%	0.00%
Reverse stock split conversion ratio									10
Fair value of stock options granted during period | $									$ 2,400	$ 2,600	$ 4,400
Weighted average grant date fair value | $ / shares									$ 28.66	$ 29.89	$ 28.81
Intrinsic value of options exercised | $									$ 5,000	$ 12,800	$ 10,500
Proceeds from stock options exercised | $									3,400	$ 1,000	$ 3,200
Unrecognized compensation costs, not probable | $									$ 10,600
Weighted average purchase price of shares purchased | $ / shares									$ 16.19	$ 18.10	$ 18.14
Preferred stock, shares issued (in shares)									0	0
Preferred stock, par value (in dollars per share) | $ / shares									$ 0.01	$ 0.01
Payments of stock issuance costs | $									$ 214	$ 0	$ 0
Series X Convertible Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion to common stock (in shares)		122,000
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares issued									0	0
Conversion to common stock (in shares)		1,508,964
Scil Animal Care Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payments to acquire business | $			$ 110,300	$ 111,000
Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares issued (in shares)				122,000
Preferred stock, par value (in dollars per share) | $ / shares				$ 0.01
Sale of stock, price per share (in dollars per share) | $ / shares				$ 1,000
Sale of stock, consideration received per transaction | $				$ 122,000
Payments of stock issuance costs | $				$ 200
Convertible preferred stock, shares issuable upon conversion (in shares)				12.4
Preferred stock, convertible, conversion price (in dollars per share) | $ / shares				$ 80.85
Conversion to common stock (in shares)									(122,000)
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount | $									$ 5,500
Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)									1 year
Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)									4 years
Stock options and restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised | $									$ 28,900
Total unrecognized compensation expense related to outstanding stock options | $									$ 3,600
Period for recognition of unrecognized compensation expense									1 year 7 months 17 days
Intrinsic value of options outstanding | $									$ 41,100
Granted at Market (in dollars per share) | $ / shares									$ 69.27
Forfeitures in period (in shares)									42,307
Options outstanding (in shares)									464,232	536,315
Outstanding exercise price (in dollars per share) | $ / shares									$ 57.18	$ 54.86
Exercises in period (in shares)									84,335
Incentive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of fair value for options granted									100.00%
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock options granted during period | $									$ 6,000
Total unrecognized compensation expense related to outstanding stock options | $									$ 2,400
Period for recognition of unrecognized compensation expense									1 year 9 months 18 days
Intrinsic value of options outstanding | $									$ 18,600
Grants in period (in shares)	240,000
Granted at Market (in dollars per share) | $ / shares	$ 60.94								$ 25.04
Forfeitures in period (in shares)									20,000
Options outstanding (in shares)									220,000
Outstanding exercise price (in dollars per share) | $ / shares									$ 60.94
Weighted average remaining contractual term (in years)									9 years 3 months 14 days
Exercises in period (in shares)									0
Performance shares not meeting performance targets (in shares)									80,000
Unrecognized compensation costs, not probable | $									$ 2,000
Performance Shares | Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)	230,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued during period									10,069	10,698	10,078
Share Purchase Plan 1997
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of share to be repurchased					300,000	250,000	500,000	250,000
Number of shares authorized to be repurchased annually								45,000
Remaining number of shares authorized to be repurchased									151,605
Common stock, shares issued									3,859
Share Purchase Plan 2003
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized												239,050
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares not meeting performance targets									129,000
Weighted average purchase price of shares purchased | $ / shares									$ 87.29	$ 74.93	$ 71.77
Restricted stock vested, fair value | $									$ 5,000	$ 300	$ 4,400