STOCK-BASED PLANS (Summary of Stock Option Activity) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 09, 2010
Stock Options
Shares of common stock reserved for issuance				3,698,050
Stock options outstanding at the beginning of the period (in shares)	1,176,640	1,086,040	1,046,490
Granted (in shares)	58,000	162,100	117,000
Exercised (in shares)	(395,482)	(3,000)
Forfeited (in shares)	(54,976)	(68,500)	(77,450)
Expired (in shares)	(1,000)
Stock options outstanding at the end of the period (in shares)	783,182	1,176,640	1,086,040
Stock options exercisable at the end of the period (in shares)	306,182
Remaining unvested options outstanding and expected to vest (in shares)	772,990
Weighted Average Exercise Price
Stock options outstanding at the beginning of the period (in dollars per share)	$ 78.87	$ 77.11	$ 72.61
Granted (in dollars per share)	119.85	109.42	134.24
Exercised (in dollars per share)	58.81	60.33
Forfeited (in dollars per share)	105.17	122.93	103.84
Expired (in dollars per share)	57.77
Stock options outstanding at the end of the period (in dollars per share)	90.22	$ 78.87	$ 77.11
Stock options exercisable at the end of the period (in dollars per share)	59.96
Stock options expected to vest at the end of the period (in dollars per share)	$ 59.96
Weighted average remaining contractual term of stock options outstanding	5 years 8 months 12 days
Weighted average remaining contractual term of stock options exercisable	3 years 7 months 6 days
Weighted average remaining contractual term of stock options expected to vest	5 years 8 months 12 days
Aggregate intrinsic value	$ 33,454,510
Aggregate intrinsic value of stock options exercisable	21,833,176
Aggregate intrinsic value of stock options expected to vest	33,302,071
Significant assumptions used in Black-Scholes option-pricing model
Stock based compensation expense	$ 7,385,000	$ 6,707,000	$ 7,284,000
Maximum
Stock Options
Maximum number of shares available for future grant	2,032,473
Stock Options
Stock Options
Share based compensation costs capitalized	$ 1,100,000	$ 2,600,000	$ 2,500,000
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 90.22
Number Outstanding (in shares)	783,182
Weighted Average Remaining Contractual Term	5 years 8 months 12 days
Number Exercisable (in shares)	306,182
Significant assumptions used in Black-Scholes option-pricing model
Weighted average grant date fair value (in dollars per share)	$ 34.51	$ 36.55	$ 44.45
Weighted-average expected life of options	8 years 4 months 24 days	7 years 4 months 24 days	7 years 6 months
Weighted-average risk-free interest rate (as a percent)	2.20%	1.80%	2.00%
Weighted-average expected volatility (as a percent)	22.80%	33.10%	26.10%
Expiration period	10 years
Unamortized stock option expense	$ 7,900,000
Stock based compensation expense	$ 8,400,000	$ 9,400,000	$ 9,800,000
Stock Options | Minimum
Significant assumptions used in Black-Scholes option-pricing model
Exercisable period	5 years
Stock Options | General and Administrative Expense
Significant assumptions used in Black-Scholes option-pricing model
Stock based compensation expense	$ 1,600,000	$ 2,900,000	$ 2,600,000
Stock Options | $46.49 - 55.82
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 51.39
Number Outstanding (in shares)	23,290
Weighted Average Remaining Contractual Term	3 years 8 months 12 days
Number Exercisable (in shares)	23,290
Stock Options | $46.49 - 55.82 | Minimum
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 46.49
Stock Options | $46.49 - 55.82 | Maximum
Exercise price range of stock options
Exercise Price (in dollars per share)	55.82
Stock Options | $57.77 - 60.33
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 58.06
Number Outstanding (in shares)	242,418
Weighted Average Remaining Contractual Term	3 years 3 months 18 days
Number Exercisable (in shares)	242,418
Stock Options | $57.77 - 60.33 | Minimum
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 57.77
Stock Options | $57.77 - 60.33 | Maximum
Exercise price range of stock options
Exercise Price (in dollars per share)	60.33
Stock Options | $61.64 - 69.75
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 65.93
Number Outstanding (in shares)	109,550
Weighted Average Remaining Contractual Term	4 years 4 months 24 days
Number Exercisable (in shares)	29,550
Stock Options | $61.64 - 69.75 | Minimum
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 61.64
Stock Options | $61.64 - 69.75 | Maximum
Exercise price range of stock options
Exercise Price (in dollars per share)	69.75
Stock Options | $81.80 - 110.50
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 98.13
Number Outstanding (in shares)	94,424
Weighted Average Remaining Contractual Term	6 years 1 month 6 days
Number Exercisable (in shares)	9,024
Stock Options | $81.80 - 110.50 | Minimum
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 81.80
Stock Options | $81.80 - 110.50 | Maximum
Exercise price range of stock options
Exercise Price (in dollars per share)	110.50
Stock Options | $112.64 - 151.72
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 124.07
Number Outstanding (in shares)	313,500
Weighted Average Remaining Contractual Term	8 years
Number Exercisable (in shares)	1,900
Stock Options | $112.64 - 151.72 | Minimum
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 112.64
Stock Options | $112.64 - 151.72 | Maximum
Exercise price range of stock options
Exercise Price (in dollars per share)	$ 151.72