EQUITY (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock-based compensation
Number of shares reserved to be granted under the plan	2,000,000
Number of Options
Exercised (in shares)	(87,378)	(43,034)	(303,536)
Treasury Stock
Shares Repurchased	37,567	34,293	163,222
Aggregate Cost	$ 2,705,000	$ 2,160,000	$ 8,103,000
Average Repurchase Price (in dollars per share)	$ 72.01	$ 63.01	$ 49.64
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)	351,253	401,287
Granted (in shares)	5,000
Exercised (in shares)	(87,378)	(43,034)
Forfeited- Unvested (in shares)		(7,000)
Outstanding at the end of the period (in shares)	268,875	351,253	401,287
Vested and expected to vest at the end of the period (in shares)	268,011	351,142
Exercisable at the end of the period (in shares)	248,875	290,128
Weighted Avg. Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 36.55	$ 36.63
Granted (in dollars per share)	71.43
Exercised (in dollars per share)	32.14	37.68
Forfeited- Unvested (in dollars per share)		34.22
Outstanding at the end of the period (in dollars per share)	38.64	36.55	$ 36.63
Vested and expected to vest at the end of the period (in dollars per share)	38.53	36.56
Exercisable at the end of the period (in dollars per share)	$ 38.05	$ 36.81
Weighted Average Remaining Contractual Term
Outstanding	4 years 8 months 12 days	5 years
Vested and expected to vest	4 years 8 months 12 days	5 years
Exercisable	4 years 6 months	4 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding	$ 10,646,006	$ 10,901,529
Vested and expected to vest	10,640,134	10,987,590
Exercisable	9,998,956	8,929,815
Unamortized stock based compensation
Unamortized stock based compensation	$ 200,000
Weighted-average period for recognition of unamortized stock-based compensation cost	2 years 7 months 10 days
Stock-based compensation, additional disclosures
Weighted-average fair value of options granted (in dollars per share)	$ 30.70
Aggregate intrinsic value of options exercised	$ 3,488,000	1,098,000	$ 6,111,000
Cash proceeds received upon exercise of options	1,999,000	1,621,000	2,669,000
Excess tax benefits from share-based compensation	$ 1,423,000	513,000	2,101,000
Weighted-average assumptions using Black-Scholes option-pricing model for estimating fair value of each option granted
Risk-free interest rate (as a percent)	1.55%
Expected dividend yield (as a percent)	1.76%
Expected life	6 years 3 months
Expected volatility (as a percent)	51.85%
Stock compensation expense
Stock compensation expense	$ 400,000	900,000	$ 1,400,000
Restricted Stock
Stock-based compensation
Vesting period	4 years
Number of Options
Granted (in shares)	93,864		100,902
Unamortized stock based compensation
Unamortized stock based compensation	$ 9,400,000
Weighted-average period for recognition of unamortized stock-based compensation cost	2 years 7 months 6 days
Stock compensation expense
Stock compensation expense	$ 4,300,000	$ 3,400,000	$ 3,100,000
Shares
Unvested at the beginning of the period (in shares)	195,143	154,519
Granted (in shares)	93,864	109,318
Forfeited (in shares)	(1,687)	(8,500)
Vested and issued (in shares)	(68,919)	(60,194)
Unvested at the end of the period (in shares)	218,401	195,143	154,519
Weighted Avg. Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 55.13	$ 44.04
Granted (in dollars per share)	66.26	64.73
Forfeited (in dollars per share)	65.18	51.44
Vested and issued (in dollars per share)	52.70	44.61
Unvested at the end of the period (in dollars per share)	$ 60.60	$ 55.13	$ 44.04
2008 Equity Incentive Plan | Restricted Stock
Stock-based compensation
Vesting period	4 years