STOCK-BASED COMPENSATION (Details) | 3 Months Ended | 9 Months Ended |
Sep. 30, 2018USD ($)$ / sharesshares | Sep. 30, 2017USD ($) | Sep. 30, 2018USD ($)Integer$ / sharesshares | Sep. 30, 2017USD ($) |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | |
Allocated Share-based Compensation Expense | $ | | | | $ (4,503,000) | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [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, 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) | | | | 86,836 | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | 2018 Awards [Member] | | | | | |
Weighted Average Grant Date Fair Value [Abstract] | | | | | |
Equity Instruments other than options, number of plans | Integer | | | | 1 | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | 2017 Awards [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] | 2018 Awards [Member] | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | | | | $ 95.19 | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | | | |
Granted (in shares) | | | | 7,884 | |
Weighted Average Grant Date Fair Value [Abstract] | | | | | |
Granted (per share) | $ / shares | | | | $ 95.19 | |
Share Based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting Rights (% vesting per year in future years) | | | | 25.00% | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Service Condition Only Awards [Member] | Executive Officer [Member] | 2017 Awards [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% | |
Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Service Condition Only Awards [Member] | Non Executive Officers [Member] | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | | | | | |
Granted (in shares) | | | | 12,425 | |
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 | $ | | $ 365,000 | $ 308,000 | $ 824,000 | $ 1,177,000 |
Allocated Share-based Compensation Expense | $ | | $ 1,574,000 | 1,319,000 | $ 3,725,000 | 4,952,000 |
Shares withheld for tax obligations | | | | 23,824 | |
Fair value of shares vested as of the vesting date | $ | | | | $ 5,149,000 | |
Award Recipient Type Employee [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Non Executive Officers [Member] | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | | | | $ 95.17 | |
Weighted Average Grant Date Fair Value [Abstract] | | | | | |
Granted (per share) | $ / shares | | | | $ 95.17 | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | 20.00% | |
Award Recipient Type Employee [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Company Performance Awards [Member] | Executive Officer [Member] | 2018 Awards [Member] | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | |
Grant date fair value of shares issued (in dollars per share) | $ / shares | | | | $ 95.19 | |
Weighted Average Grant Date Fair Value [Abstract] | | | | | |
Granted (per share) | $ / shares | | | | $ 95.19 | |
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 | | | | 20.00% | |
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights | | | | 20.00% | |
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) | | | | 24,690 | |
Award Recipient Type Employee [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Company Performance Awards [Member] | Executive Officer [Member] | 2017 Awards [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] | 2018 Awards [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 | | | | 20.00% | |
Share Based Compensation Arrangement By Share Based Payment Award Possible Shares To Be Awarded Vesting Rights | | | | 20.00% | |
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) | | | | 6,173 | |
Award Recipient Type Employee [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Individual performance awards [Member] | Executive Officer [Member] | 2017 Awards [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],[2] | $ 0 | | $ 84.09 | |
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) | | 143,596 | | 152,926 | |
Granted (in shares) | [1],[2] | 0 | | 50,217 | |
Forfeited (in shares) | | 0 | | 0 | |
Vested (in shares) | | (71) | | (59,618) | |
Unvested at end of period (in shares) | | 143,525 | | 143,525 | |
Weighted Average Grant Date Fair Value [Abstract] | | | | | |
Unvested at beginning of period (per share) | $ / shares | | $ 70.30 | | $ 63.22 | |
Granted (per share) | $ / shares | [1],[2] | 0 | | 84.09 | |
Forfeited (per share) | $ / shares | | 0 | | 0 | |
Vested (per share) | $ / shares | | 88.86 | | 63.80 | |
Unvested at end of period (per share) | $ / shares | | $ 70.29 | | $ 70.29 | |
Award Recipient Type Director [Member] | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | |
Allocated Share-based Compensation Expense | $ | | $ 1,000 | $ 168,000 | $ 1,132,000 | $ 491,000 |
One year period [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | 2017 Awards [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] | 2017 Awards [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] | 2018 Awards [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) | | | | 27,596 | |
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Shareholder Return Awards [Member] | Executive Officer [Member] | 2017 Awards [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 | |
| |
[1] | (1) Includes shares granted in prior years for which performance conditions have been satisfied and the number of shares have been determined. | |
[2] | Does not include the restricted shares that may be earned if the performance goals established in 2017 for long-term performance and in 2018 for annual and long-term performance are achieved. Depending on the actual level of achievement of the goals at the end of the open performance periods, the number of shares earned could range from zero to 86,836. | |