STOCK-BASED COMPENSATION (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Compensation Plan disclosure [Abstract]
Stock-based compensation cost	$ 8,423,000	$ 6,567,000	$ 5,540,000
Award Recipient Type Employee [Member] | Restricted Stock [Member]
Stock Compensation Plan disclosure [Abstract]
Stock-based compensation cost	7,891,000	6,071,000	5,087,000
Stock based compensation cost capitalized as development costs	$ 1,672,000	$ 1,415,000	$ 1,253,000
Share awards granted (in shares)	100,622	71,642	112,099
Grant date fair value of shares issued (in dollars per share)	$ 61.07	$ 61.96	$ 56.77
Compensation is recognized over a weighted average period (in years)	2 years 8 months 12 days
Share based compensation, share based payment arrangements other than stock options, unrecognized cost associated with awards not yet vested	$ 5,080,000
Shares withheld to satisfy the tax obligations (in shares)	32,409	31,673	9,412
Fair value of shares granted	$ 6,145,000	$ 4,439,000	$ 6,364,000
Fair value of shares vested as of the vesting date	$ 6,664,000	$ 5,712,000	$ 1,700,000
Restricted Stock Activity [Roll Forward]
Unvested at beginning of year (in shares)	265,911	293,989	212,206
Granted (in shares)	100,622	71,642	112,099
Forfeited (in shares)	0	(2,375)	0
Vested (in shares)	(105,835)	(97,345)	(30,316)
Unvested at end of year (in shares)	260,698	265,911	293,989
Restricted stock activity weighted average price [Abstract]
Unvested at beginning of year (in dollars per share)	$ 49.79	$ 47.17	$ 42.84
Granted (in dollars per share)	61.07	61.96	56.77
Forfeited (in dollars per share)	0.00	52.72	0.00
Vested (in dollars per share)	53.40	50.76	52.32
Unvested at end of year (in dollars per share)	$ 52.68	$ 49.79	$ 47.17
Nonvested Shares Vesting Schedule [Abstract]
2016 (in shares)				139,333
2017 (in shares)				41,138
2018 (in shares)				31,215
2019 (in shares)				24,507
2020 (in shares)				24,505
Total Nonvested Shares (in shares)	265,911	293,989	212,206	260,698	265,911	293,989
Award Recipient Type Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual Director Retainer Stock Award Amount				$ 75,000
Stock Compensation Plan disclosure [Abstract]
Stock-based compensation cost	$ 514,000	$ 490,000	$ 395,000
Award Recipient Type Director [Member] | Restricted Stock [Member]
Stock Compensation Plan disclosure [Abstract]
Fair value of shares vested as of the vesting date	$ 6,000	$ 7,000
Directors Equity Plan 2005 [Member]
Stock Compensation Plan disclosure [Abstract]
Authorized shares of common stock (in shares)				50,000
Management Incentive Plan 2004 [Member]
Stock Compensation Plan disclosure [Abstract]
Authorized shares of common stock (in shares)				1,900,000
Equity Incentive Plan 2013 [Member]
Stock Compensation Plan disclosure [Abstract]
Authorized shares of common stock (in shares)				2,000,000
Shares available for grant (in shares)				1,802,000	1,900,800	1,971,164
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Company Performance Awards [Member] | Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of vesting that occurred on grant date	20.00%
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)	42,447
Grant date fair value of shares issued (in dollars per share)	$ 61.13
Percentage of shares granted vesting annually in future periods (in hundredths)				20.00%
Restricted Stock Activity [Roll Forward]
Granted (in shares)	42,447
Restricted stock activity weighted average price [Abstract]
Granted (in dollars per share)	$ 61.13
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of vesting that occurred on grant date	25.00%
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)	34,650
Grant date fair value of shares issued (in dollars per share)	$ 61.13
Percentage of shares granted vesting annually in future periods (in hundredths)				25.00%
Restricted Stock Activity [Roll Forward]
Granted (in shares)	34,650
Restricted stock activity weighted average price [Abstract]
Granted (in dollars per share)	$ 61.13
Equity Incentive Plan 2013 [Member] | Award Recipient Type Employee [Member] | Restricted Stock [Member] | Non Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)	23,525
Grant date fair value of shares issued (in dollars per share)	$ 60.89
Restricted Stock Activity [Roll Forward]
Granted (in shares)	23,525
Restricted stock activity weighted average price [Abstract]
Granted (in dollars per share)	$ 60.89
Equity Incentive Plan 2013 [Member] | Award Recipient Type Employee [Member] | Restricted Stock [Member] | Company Performance Awards [Member] | Executive Officer [Member]
Stock Compensation Plan disclosure [Abstract]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (maximum)	49,366
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (minimum)	0
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of future vesting that will occur on grant date	20.00%
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights	20.00%
Equity Incentive Plan 2013 [Member] | Award Recipient Type Employee [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member]
Stock Compensation Plan disclosure [Abstract]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (maximum)	51,432
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Potential Grants in Future Period (minimum)	0
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of future vesting that will occur on grant date	25.00%
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights	25.00%
Equity Incentive Plan 2013 [Member] | Award Recipient Type Director [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangements by share-based payment award, equity instruments other than options, percent of vesting that occurred during period	25.00%
Share Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting Rights (% vesting per year in future years)	25.00%
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)			417
Grant date fair value of shares issued (in dollars per share)			$ 59.97
Restricted Stock Activity [Roll Forward]
Granted (in shares)			417
Restricted stock activity weighted average price [Abstract]
Granted (in dollars per share)			$ 59.97
Award Recipient Type Director [Member]
Stock Compensation Plan disclosure [Abstract]
Shares issued to directors (in shares)	9,373	7,742	7,469
New Director Stock Awards to be Issued in Future Periods [Member] | Award Recipient Type Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New Director Restricted Stock Award Amount to be Awarded in Future Periods	$ 25,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Director stock option [Member]
Stock Compensation Plan disclosure [Abstract]
Intrinsic value realized by employees or directors from the exercise of options			$ 172,000
Stock Options [Roll Forward]
Outstanding at beginning of year (in shares)	0	0	4,500
Exercised (in shares)	0	0	(4,500)
Outstanding at end of year (in shares)	0	0	0
Exercisable at end of year (in shares)				0	0	0
Stock Options weighted average price [Abstract]
Outstanding at beginning of year (in dollars per share)	$ 0.00	$ 0.00	$ 26.60
Exercised (in dollars per share)	0.00	0.00	26.60
Outstanding at end of year (in dollars per share)	0.00	0.00	26.60	$ 0.00	$ 0.00	$ 0.00
Stock options exercisable [Abstract]
Exercisable at end of year (in dollars per share)	$ 0.00	$ 0.00	$ 0.00