STOCK PLANS (Details 4) (Stock options, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock options
Number of Options
Outstanding at beginning of year (in shares)	1,023,389	1,364,284	1,540,193
Granted (in shares)			20,000
Exercised (in shares)	(375,718)	(330,895)	(93,839)
Expired (in shares)			(37,070)
Forfeited (in shares)		(10,000)	(65,000)
Outstanding at end of year (in shares)	647,671	1,023,389	1,364,284
Exercisable at end of year (in shares)	635,671
Weighted-Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 14.48	$ 13.84	$ 13.83
Granted (in dollars per share)			$ 15.98
Exercised (in dollars per share)	$ 12.93	$ 11.98	$ 11.09
Expired (in dollars per share)			$ 16.34
Forfeited (in dollars per share)		$ 10.24	$ 16.76
Outstanding at end of year (in dollars per share)	$ 15.37	$ 14.48	$ 13.84
Exercisable at end of year (in dollars per share)	$ 15.36
Weighted- Average Remaining Contractual Life (years)
Outstanding at end of year	2 years 1 month 28 days	2 years 8 months 16 days	3 years 6 months 11 days
Exercisable at end of year	2 years 0 months 26 days
Aggregate Intrinsic Value
Outstanding at beginning of year	$ 4,625,520	$ 3,686,098	$ 3,631,381
Granted			0
Exercised	2,237,704	1,739,700	426,278
Expired			37,070
Forfeited		42,400	76,425
Outstanding at end of year	4,016,809	4,625,520	3,686,098
Exercisable at end of year	$ 3,954,529