Represents the additional expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

No definition available.

EQUITY (Details) - USD ($)	12 Months Ended			144 Months Ended
EQUITY (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 18, 2016	Sep. 19, 2016	Sep. 30, 2004
Stock-based compensation
Number of shares reserved to be granted under the plan	2,000,000
Number of shares available for grant	801,000
Treasury Stock
Shares Repurchased	171,907	234,746	70,686
Aggregate Cost	$ 12,437,000	$ 12,983,000	$ 4,873,000
Shares repurchased to satisfy tax withholdings and exercise obligations	141,180	32,814	38,279
Aggregate cost to satisfy tax withholdings and exercise obligations	$ 10,859,000	$ 2,348,000	$ 2,775,000
Average Repurchase Price (in dollars per share)	$ 76.76	$ 71.54	$ 72.50
Number of Options
Exercised (in shares)	(158,021)	(35,081)	(43,053)
Stock-based compensation, additional disclosures
Cash proceeds received upon exercise of options	$ 72,000	$ 1,030,000	$ 649,000
2004 Repurchase Plan
Treasury Stock
Authorized amount						$ 5,000,000
Aggregate Cost				$ 4,100,000
2016 Repurchase Plan
Treasury Stock
Authorized amount					$ 50,000,000
Value of shares available for repurchase	$ 37,700,000
2004 and 2016 Repurchase Plan
Treasury Stock
Shares Repurchased	30,427	201,932	32,407
Aggregate Cost	$ 1,577,000	$ 10,636,000	$ 2,195,000
Average Repurchase Price (in dollars per share)	$ 51.82	$ 52.67	$ 64.72
Stock options
Stock-based compensation
Expiration term	10 years
Vesting period	4 years
Number of Options
Outstanding at the beginning of the period (in shares)	200,021	225,822
Granted (in shares)	0	10,000
Exercised (in shares)	(158,021)	(35,801)
Outstanding at the end of the period (in shares)	42,000	200,021	225,822
Vested and expected to vest at the end of the period (in shares)	42,000	200,021
Exercisable at the end of the period (in shares)	33,250	187,521
Weighted Avg. Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 41.76	$ 39.77
Granted (in dollars per share)		52.97
Exercised (in dollars per share)	39.95	32.29
Outstanding at the end of the period (in dollars per share)	48.61	41.76	$ 39.77
Vested and expected to vest at the end of the period (in dollars per share)	48.61	41.76
Exercisable at the end of the period (in dollars per share)	$ 46.76	$ 40.77
Weighted Average Remaining Contractual Term
Outstanding	4 years 1 month 6 days	3 years 7 months 6 days
Vested and expected to vest	4 years 1 month 6 days	3 years 7 months 6 days
Exercisable	3 years	3 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding	$ 823,515	$ 2,780,253
Vested and expected to vest	962,840	2,780,253
Exercisable	823,515	$ 2,757,353
Unamortized stock based compensation
Unamortized stock based compensation	$ 100,000
Weighted-average period for recognition of unamortized stock-based compensation cost	2 years 3 months 18 days
Stock-based compensation, additional disclosures
Weighted-average fair value of options granted (in dollars per share)		$ 13.77
Aggregate intrinsic value of options exercised	$ 5,927,000	$ 936,000	$ 1,591,000
Cash proceeds received upon exercise of options	72,000	$ 1,030,000	649,000
Excess tax benefits from share-based compensation			591,000
Weighted-average assumptions using Black-Scholes option-pricing model for estimating fair value of each option granted
Risk-free interest rate (as a percent)		1.79%
Expected dividend yield (as a percent)		1.28%
Expected life		4 years
Expected volatility (as a percent)		34.01%
Stock compensation expense
Stock compensation expense	$ 100,000	$ 100,000	100,000
Restricted Stock
Stock-based compensation
Vesting period	4 years
Unamortized stock based compensation
Unamortized stock based compensation	$ 9,000,000
Weighted-average period for recognition of unamortized stock-based compensation cost	2 years 6 months
Stock compensation expense
Stock compensation expense	$ 6,100,000	6,600,000	6,200,000
Additional compensation expenses	$ 200,000	$ 300,000	$ 100,000
Shares
Unvested at the beginning of the period (in shares)	214,938	229,040
Granted (in shares)	111,474	95,095	100,005
Forfeited (in shares)	(31,327)	(12,074)
Vested and issued (in shares)	(94,432)	(97,123)
Unvested at the end of the period (in shares)	200,653	214,938	229,040
Weighted Avg. Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 68.62	$ 67.13
Granted (in dollars per share)	59.52	68.09
Forfeited (in dollars per share)	66.53	69.71
Vested and issued (in dollars per share)	66.27	64.01
Unvested at the end of the period (in dollars per share)	$ 65.21	$ 68.62	$ 67.13