STOCK-BASED COMPENSATION AND EMPLOYEE BENEFIT PLANS - EMPLOYEE STOCK PURCHASE PLAN (Details) (USD $)	12 Months Ended				12 Months Ended										12 Months Ended				12 Months Ended
	Dec. 31, 2013 persons	Dec. 31, 2012	Dec. 31, 2011	May 31, 1995	Dec. 31, 2013 United States Defined Contribution Plan	Dec. 31, 2012 United States Defined Contribution Plan	Dec. 31, 2011 United States Defined Contribution Plan	Dec. 31, 2013 Canadian Defined Contribution Plan	Dec. 31, 2012 Canadian Defined Contribution Plan	Dec. 31, 2011 Canadian Defined Contribution Plan	Dec. 31, 2013 Fair Value, Inputs, Level 1	Dec. 31, 2012 Fair Value, Inputs, Level 1	Dec. 31, 2013 Fair Value, Inputs, Level 2	Dec. 31, 2012 Fair Value, Inputs, Level 2	Dec. 31, 2013 2005 Employee Stock Purchase Plan	Dec. 31, 2012 2005 Employee Stock Purchase Plan	Dec. 31, 2005 2005 Employee Stock Purchase Plan	May 31, 1995 2005 Employee Stock Purchase Plan	Dec. 31, 2013 Last Day of the quarterly Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan, Number of Shares Authorized																		2,000,000
Quarterly Offerings of Shares				100,000
Share Based Compensation Arrangement By Share Based Payment Award, Additional Shares Authorized																	1,000,000
Common Stock, Capital Shares Reserved for Future Issuance															340,780
Maximum Employee Subscription Rate															10.00%
Payroll Deduction to Purchase Common Stock															85.00%				85.00%
Discount from Market Price at Offering Date															15.00%
Weighted Average per Share Fair Values of the Purchase Rights (in dollars per share)															$ 9.61	$ 10.29
Number of active non-supervisory Canadian employees	20
Defined Benefit Plan, Net Periodic Benefit Cost	$ 300,000	$ 300,000	$ 200,000
Pension assets measured at fair value	9,453,000	8,630,000									7,591,000	6,524,000	1,862,000	2,106,000
Defined Benefit Plan, Benefit Obligation	10,307,000	9,909,000
Defined Contribution Plan, Cost Recognized					$ 8,900,000	$ 4,800,000	$ 3,900,000	$ 3,100,000	$ 2,100,000	$ 1,600,000