STOCK COMPENSATION PLANS (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock purchase plan
Compensation expense recognized	$ 13,900,000	$ 13,500,000	$ 12,700,000
Shares available under the Purchase Plan	3,715,327
Stock Options
Summary of stock option activity
Outstanding at beginning of year (in shares)	406,731
Exercised (in shares)	(234,101)
Forfeited (in shares)	(130,514)
Outstanding at end of year (in shares)	42,116	406,731
Vested or expected to vest at year-end (in shares)	42,116
Exercisable at year-end	42,116
Outstanding at beginning of year, weighted average exercise price (in dollars per share)	$ 26.72
Exercised, weighted average exercise price (in dollars per share)	$ 21.09
Forfeited, weighted average exercise price (in dollars per share)	$ 38.76
Outstanding at end of year, weighted average exercise price (in dollars per share)	$ 20.75	$ 26.72
Vested or expected to vest at year-end, weighted average exercise price (in dollars per share)	$ 20.75
Exercisable at end year-end, weighted average exercise price (in dollars per share)	$ 20.75
Outstanding at end of year, weighted average remaining term	2 months 8 days
Vested or expected to vest at end of year, weighted average remaining term	2 months 8 days
Exercisable at end of year, weighted average remaining term	2 months 8 days
Outstanding at end of year, aggregate intrinsic value	757,000
Vested or expected to vest at year-end, aggregate intrinsic value	757,000
Exercisable at year-end, aggregate intrinsic value	757,000
Share based compensation plan, additional disclosures
Total intrinsic value of options exercised (in thousands)	3,546,000	926,000	978,000
Total fair value of options vested (in thousands)		363,000	3,717,000
Stock Options | Minimum
Stock Options
Vesting period	3 years
Contractual term of stock option grants	7 years
Stock Options | Maximum
Stock Options
Vesting period	4 years
Contractual term of stock option grants	10 years
Stock Purchase Plan
Stock purchase plan
Purchase price of shares in terms compared to market price per share (as a percent)	90.00%
Value of shares sold to employees under purchase plan	25,000
Compensation expense recognized	0
Common stock, shares authorized (in shares)	2,000,000
Shares sold to employees under purchase plan (in shares)	58,587	53,015
Stock Issued During Period, Value, Employee Stock Purchase Plan	$ 1,900,000	$ 1,400,000
Shares available under the Purchase Plan	694,713