STOCK AWARD PLANS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
STOCK AWARD PLANS [Abstract]
Compensation cost	$ 2,693	$ 2,584
Income tax benefit	881	969
Share based Compensation Plans Combined Disclosure [Abstract]
Intrinsic value of stock options exercised	1,267	0
Tax benefit from stock options exercised	414
Intrinsic value of restricted stock vesting	6,989	5,432
Tax benefit from restricted stock vesting	2,285	2,037
Fair value of options vested	2,473	2,469
Fair value of restricted stock vested	$ 6,989	$ 5,432
Fair value of stock options granted (in dollars per share)	$ 20.65	$ 15.61
Fair value of stock options granted	$ 2,517	$ 2,430
Stock Options [Member]
Share based Compensation Plans Combined Disclosure [Abstract]
Unrecognized compensation cost related to unvested awards	$ 5,245
Weighted average period of recognition in years	2 years
Fair Value Assumptions [Abstract]
Dividend yield	0.00%	0.00%
Average risk-free interest rate	2.00%	1.50%
Stock price volatility	27.00%	29.00%
Estimated option term	6 years	6 years
Restricted Stock [Member]
Share based Compensation Plans Combined Disclosure [Abstract]
Unrecognized compensation cost related to unvested awards	$ 24,268
Weighted average period of recognition in years	3 years 8 months 12 days
Employee Stock Award Plan [Member]
Stock Award Plan Information [Abstract]
Term of grant	7 years
Vesting period	3 years
Shares available for future grants (in shares)	1,745,801
Employee Stock Award Plan [Member] | Stock Options [Member]
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period Start, (in shares)	601,121
Granted (in shares)	121,908
Exercised (in shares)	(16,910)
Outstanding at Period End (in shares)	706,119
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share)	$ 65.33
Granted (in dollars per share)	68.50
Exercised (in dollars per share)	32.82
Outstanding at Period End (in dollars per share)	66.66
Employee Stock Award Plan [Member] | Stock Options [Member] | First Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	51.23
Range of Exercise Prices, lower limit (in dollars per share)	$ 46.74
Options Outstanding [Abstract]
Number Outstanding (in shares)	212,335
Weighted Average Remaining Contractual Life	4 years 6 months
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 50.03
Options Exercisable [Abstract]
Number Exercisable (in shares)	108,531
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 48.89
Employee Stock Award Plan [Member] | Stock Options [Member] | Second Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	74.99
Range of Exercise Prices, lower limit (in dollars per share)	$ 64.89
Options Outstanding [Abstract]
Number Outstanding (in shares)	424,643
Weighted Average Remaining Contractual Life	4 years 8 months 12 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 69.78
Options Exercisable [Abstract]
Number Exercisable (in shares)	237,022
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 70.31
Employee Stock Award Plan [Member] | Stock Options [Member] | Third Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	96.85
Range of Exercise Prices, lower limit (in dollars per share)	$ 93.64
Options Outstanding [Abstract]
Number Outstanding (in shares)	33,987
Weighted Average Remaining Contractual Life	3 years 9 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 94.31
Options Exercisable [Abstract]
Number Exercisable (in shares)	33,987
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 94.31
Employee Stock Award Plan [Member] | Stock Options [Member] | Fourth Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	104.37
Range of Exercise Prices, lower limit (in dollars per share)	$ 101.46
Options Outstanding [Abstract]
Number Outstanding (in shares)	35,154
Weighted Average Remaining Contractual Life	3 years 10 months 24 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 102.60
Options Exercisable [Abstract]
Number Exercisable (in shares)	35,154
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 102.60
Employee Stock Award Plan [Member] | Stock Options [Member] | Full Exercise Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	104.37
Range of Exercise Prices, lower limit (in dollars per share)	$ 46.74
Options Outstanding [Abstract]
Number Outstanding (in shares)	706,119
Weighted Average Remaining Contractual Life	4 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 66.66
Aggregate Intrinsic Value, Options Outstanding	$ 5,155
Options Exercisable [Abstract]
Number Exercisable (in shares)	414,694
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 69.41
Aggregate Intrinsic Value, Options Exercisable	$ 2,724
Employee Stock Award Plan [Member] | Restricted Stock [Member]
Unvested Restricted Stock Award Shares [Roll Forward]
Nonvested balance beginning of period (in shares)	377,655
Granted (in shares)	120,820
Vested (in shares)	(105,207)
Forfeited (in shares)	(1,017)
Nonvested balance end of period (in shares)	392,251
Weighted Average Grant Date Fair Value Per Share [Abstract]
Nonvested balance beginning of period (in dollars per share)	$ 66.14
Granted (in dollars per share)	68.50
Vested (in dollars per share)	68.90
Forfeited (in dollars per share)	64.20
Nonvested balance end of period (in dollars per share)	$ 66.13
2000 Director Plan [Member]
Stock Award Plan Information [Abstract]
Term of grant	10 years
Vesting period	6 months
Shares available for future grants (in shares)	522,457
2000 Director Plan [Member] | Stock Options [Member]
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period Start, (in shares)	205,429
Exercised (in shares)	(27,000)
Outstanding at Period End (in shares)	178,429
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share)	$ 64.60
Exercised (in dollars per share)	45.28
Outstanding at Period End (in dollars per share)	67.53
2000 Director Plan [Member] | Stock Options [Member] | First Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	$ 29.60
Options Outstanding [Abstract]
Number Outstanding (in shares)	6,000
Weighted Average Remaining Contractual Life	2 years 1 month 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 29.60
Options Exercisable [Abstract]
Number Exercisable (in shares)	6,000
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 29.60
2000 Director Plan [Member] | Stock Options [Member] | Second Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	56.45
Range of Exercise Prices, lower limit (in dollars per share)	$ 41.24
Options Outstanding [Abstract]
Number Outstanding (in shares)	65,276
Weighted Average Remaining Contractual Life	2 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 51.96
Options Exercisable [Abstract]
Number Exercisable (in shares)	65,276
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 51.96
2000 Director Plan [Member] | Stock Options [Member] | Third Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	62.48
Range of Exercise Prices, lower limit (in dollars per share)	$ 61.89
Options Outstanding [Abstract]
Number Outstanding (in shares)	35,153
Weighted Average Remaining Contractual Life	5 years 3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 62.31
Options Exercisable [Abstract]
Number Exercisable (in shares)	35,153
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 62.31
2000 Director Plan [Member] | Stock Options [Member] | Fourth Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	99.52
Range of Exercise Prices, lower limit (in dollars per share)	$ 75.17
Options Outstanding [Abstract]
Number Outstanding (in shares)	72,000
Weighted Average Remaining Contractual Life	6 years
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 87.35
Options Exercisable [Abstract]
Number Exercisable (in shares)	72,000
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 87.35
2000 Director Plan [Member] | Stock Options [Member] | Full Exercise Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	99.52
Range of Exercise Prices, lower limit (in dollars per share)	$ 29.60
Options Outstanding [Abstract]
Number Outstanding (in shares)	178,429
Weighted Average Remaining Contractual Life	4 years 3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 67.53
Aggregate Intrinsic Value, Options Outstanding	$ 1,749
Options Exercisable [Abstract]
Number Exercisable (in shares)	178,429
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 67.53
Aggregate Intrinsic Value, Options Exercisable	$ 1,749
2000 Director Plan [Member] | Restricted Stock [Member]
Unvested Restricted Stock Award Shares [Roll Forward]
Nonvested balance beginning of period (in shares)	347
Vested (in shares)	(347)
Nonvested balance end of period (in shares)	0
Weighted Average Grant Date Fair Value Per Share [Abstract]
Nonvested balance beginning of period (in dollars per share)	$ 64.89
Vested (in dollars per share)	64.89
Nonvested balance end of period (in dollars per share)	$ 0