STOCK-BASED COMPENSATION (Details) | 3 Months Ended |
Mar. 31, 2018USD ($)Integer$ / sharesshares | Mar. 31, 2017USD ($) |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | |
Allocated Share-based Compensation Expense | $ | | $ (1,044,000) | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | | | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Equity Instruments other than options, number of plans | Integer | | 3 | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Service Condition Only Awards [Member] | Executive Officer [Member] | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | | $ 78.18 | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | |
Granted (in shares) | | 5,406 | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Granted (per share) | $ / shares | | $ 78.18 | |
Equity Instruments other than options, number of plans | Integer | | 1 | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | 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% | |
Award Recipient Type Employee [Member] | Restricted Stock [Member] | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | |
Stock-based compensation costs capitalized as development costs | $ | | $ 214,000 | $ 486,000 |
Allocated Share-based Compensation Expense | $ | | $ 1,043,000 | 2,681,000 |
Shares withheld for tax obligations | | 23,824 | |
Fair value of shares vested as of the vesting date | $ | | $ 5,142,000 | |
Award Recipient Type Employee [Member] | 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] | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | | $ 78.18 | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | |
Granted (in shares) | | 21,097 | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Granted (per share) | $ / shares | | $ 78.18 | |
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of vesting that occurred on grant date | | 20.00% | |
Share Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting Rights (% vesting per year in future years) | | 20.00% | |
Award Recipient Type Employee [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Individual performance awards [Member] | Executive Officer [Member] | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | | $ 80.93 | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | |
Granted (in shares) | | 4,554 | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Granted (per share) | $ / shares | | $ 80.93 | |
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of vesting that occurred on grant date | | 20.00% | |
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights | | 20.00% | |
Award Recipient Type Employees and Directors [Member] | Restricted Stock [Member] | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | [1] | $ 76.56 | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | |
Unvested at beginning of period (in shares) | | 152,926 | |
Granted (in shares) | [1] | 29,908 | |
Forfeited (in shares) | | 0 | |
Vested (in shares) | | (59,547) | |
Unvested at end of period (in shares) | | 123,287 | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Unvested at beginning of period (per share) | $ / shares | | $ 63.22 | |
Granted (per share) | $ / shares | [1] | 76.56 | |
Forfeited (per share) | $ / shares | | 0 | |
Vested (per share) | $ / shares | | 63.77 | |
Unvested at end of period (per share) | $ / shares | | $ 66.20 | |
Award Recipient Type Director [Member] | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | |
Allocated Share-based Compensation Expense | $ | | $ 355,000 | $ 162,000 |
One year period [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | |
Granted (in shares) | | 4,257 | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of vesting that occurred on grant date | | 100.00% | |
Number of years in total shareholder return performance period | Integer | | 1 | |
Two year period [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | | | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of future vesting that will occur on performance determination date | | 100.00% | |
Number of years in total shareholder return performance period | Integer | | 2 | |
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, Potential Grants in Future Period (maximum) | | 9,460 | |
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | | | |
Weighted Average Grant Date Fair Value [Abstract] | | | |
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Percent of future vesting that will occur on performance determination date | | 75.00% | |
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights | | 25.00% | |
Number of years in total shareholder return performance period | Integer | | 3 | |
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, Potential Grants in Future Period (maximum) | | 18,917 | |
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[1] | (1) Includes shares granted in prior years for which performance conditions have been satisfied and the number of shares have been determined. | |