STOCK-BASED COMPENSATION (Details)		12 Months Ended
		Dec. 31, 2021 USD ($) Integer $ / shares shares	Dec. 31, 2020 USD ($) Integer $ / shares shares	Dec. 31, 2019 USD ($) Integer $ / shares shares		Dec. 31, 2018 $ / shares shares
Stock Compensation Plan disclosure [Abstract]
Stock-based compensation cost | $		$ 9,847,000	$ 8,502,000	$ 9,374,000
Award Recipient Type Employee [Member]
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)	[1],[2]	66,623	69,446	59,943
Restricted Stock Activity [Roll Forward]
Unvested at beginning of year (in shares)		113,125	130,884	143,314
Granted (in shares)	[1],[2]	66,623	69,446	59,943
Forfeited (in shares)		0	(440)	(3,010)
Vested (in shares)		(73,692)	(86,765)	(69,363)
Unvested at end of year (in shares)		106,056	113,125	130,884		143,314
Share Based Payment Arrangement [Abstract]
Total Unvested Shares (in shares)		106,056	113,125	130,884		143,314
Award Recipient Type Employee [Member] | Restricted Stock [Member]
Stock Compensation Plan disclosure [Abstract]
Stock-based compensation cost | $		$ 9,136,000	$ 7,605,000	$ 8,647,000
Stock based compensation cost capitalized as development costs | $		$ 2,336,000	$ 1,923,000	$ 2,536,000
Grant date fair value of shares issued (in dollars per share) | $ / shares	[1],[2]	$ 115.30	$ 101.19	$ 94.62
Compensation is recognized over a weighted average period (in years)		2 years 7 months 6 days
Share based compensation, share based payment arrangements other than stock options, unrecognized cost associated with awards not yet vested | $		$ 4,444,000
Shares withheld to satisfy the tax obligations (in shares)		30,252	36,445	28,955
Fair value of shares granted | $		$ 7,682,000	$ 7,028,000	$ 5,672,000
Fair value of shares vested as of the vesting date | $		$ 10,322,000	$ 11,754,000	$ 6,662,000
Restricted Stock Activity [Roll Forward]
Unvested at end of year (in shares)		106,056
Restricted stock activity [Abstract]
Unvested at beginning of year (in dollars per share) | $ / shares		$ 100.86	$ 82.78	$ 70.26
Granted (in dollars per share) | $ / shares	[1],[2]	115.30	101.19	94.62
Forfeited (in dollars per share) | $ / shares		0	112.14	86.19
Vested (in dollars per share) | $ / shares		91.59	73.80	66.99
Unvested at end of year (in dollars per share) | $ / shares		$ 116.37	$ 100.86	$ 82.78		$ 70.26
Share Based Payment Arrangement [Abstract]
Unvested shares in 2022 (in shares)		49,155
Unvested shares in 2023 (in shares)		33,123
Unvested shares in 2024 (in shares)		15,690
Unvested shares in 2025 (in shares)		6,248
Unvested shares in 2026 (in shares)		1,840
Total Unvested Shares (in shares)		106,056
Accrued dividends on unvested restricted stock | $		$ 1,585,000	$ 1,433,000	$ 1,618,000
Award Recipient Type Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual Director Retainer Stock Award Amount | $		100,000
Stock Compensation Plan disclosure [Abstract]
Stock-based compensation cost | $		$ 711,000	$ 897,000	$ 727,000
Share awards granted (in shares)		0	208	0
Shares issued to directors (in shares)		4,466	8,182	6,384
Restricted Stock Activity [Roll Forward]
Unvested at beginning of year (in shares)		278	140	211
Granted (in shares)		0	208	0
Forfeited (in shares)		0	0	0
Vested (in shares)		(122)	(70)	(71)
Unvested at end of year (in shares)		156	278	140		211
Share Based Payment Arrangement [Abstract]
Total Unvested Shares (in shares)		156	278	140		211
Award Recipient Type Director [Member] | Restricted Stock [Member]
Stock Compensation Plan disclosure [Abstract]
Grant date fair value of shares issued (in dollars per share) | $ / shares		$ 0	$ 120.39	$ 0
Fair value of shares vested as of the vesting date | $		$ 21,000	$ 9,000	$ 9,000
Restricted stock activity [Abstract]
Unvested at beginning of year (in dollars per share) | $ / shares		$ 112.45	$ 88.86	$ 88.86
Granted (in dollars per share) | $ / shares		0	120.39	0
Forfeited (in dollars per share) | $ / shares		0	0	0
Vested (in dollars per share) | $ / shares		102.30	88.86	88.86
Unvested at end of year (in dollars per share) | $ / shares		$ 120.39	$ 112.45	$ 88.86		$ 88.86
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)		1,477,241	1,527,382	1,583,223
Equity Incentive Plan 2013 [Member] | Long-term equity compensation awards | Service Condition Only Awards [Member] | Executive Officer [Member]
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)		7,801	7,217	9,947		7,884
Grant date fair value of shares issued (in dollars per share) | $ / shares		$ 138.93	$ 131.36	$ 105.97		$ 95.19
Restricted Stock Activity [Roll Forward]
Granted (in shares)		7,801	7,217	9,947		7,884
Restricted stock activity [Abstract]
Granted (in dollars per share) | $ / shares		$ 138.93	$ 131.36	$ 105.97		$ 95.19
Share Based Payment Arrangement [Abstract]
Grant date		Feb. 25, 2021	Mar. 06, 2020	Mar. 07, 2019		Jun. 01, 2018
Vesting period		4 years
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Company Performance Awards [Member] | Executive Officer [Member]
Stock Compensation Plan disclosure [Abstract]
Grant date fair value of shares issued (in dollars per share) | $ / shares		$ 138.93	$ 131.36	$ 105.97	[3]
Restricted stock activity [Abstract]
Granted (in dollars per share) | $ / shares		$ 138.93	$ 131.36	$ 105.97	[3]
Share Based Payment Arrangement [Abstract]
Grant date		Feb. 25, 2021	Mar. 06, 2020	Mar. 07, 2019	[3],[4]
Performance period		1/1/21 - 12/31/21	1/1/20 - 12/31/20	1/1/19 - 12/31/19	[3],[4]
Range of earnable shares - low end of range		0	0	0	[3],[4]
Range of earnable shares - high end of range		19,052	19,282	9,594	[3],[4]
Shares determined			18,380	9,162	[3]
Shares determined	[5]	N/A (3)
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Company Performance Awards [Member] | Executive Officer [Member] | FFO
Stock Compensation Plan disclosure [Abstract]
Grant date fair value of shares issued (in dollars per share) | $ / shares	[3]			$ 122.61
Restricted stock activity [Abstract]
Granted (in dollars per share) | $ / shares	[3]			$ 122.61
Share Based Payment Arrangement [Abstract]
Grant date	[3],[4],[6]			Aug. 28, 2019
Performance period	[3],[4],[6]			1/1/19 - 12/31/19
Range of earnable shares - low end of range	[3],[4],[6]			0
Range of earnable shares - high end of range	[3],[4],[6]			15,990
Shares determined	[3]			15,990
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Company Performance Awards [Member] | Executive Officer [Member] | End of the one-year performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		34.00%		20.00%
Share Based Payment Arrangement [Abstract]
Vesting period		1 year
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Company Performance Awards [Member] | Executive Officer [Member] | Following two years after performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		33.00%
Share Based Payment Arrangement [Abstract]
Vesting period		2 years
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Company Performance Awards [Member] | Executive Officer [Member] | Each of the following four years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage				20.00%
Share Based Payment Arrangement [Abstract]
Vesting period				4 years
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Individual performance awards [Member] | Executive Officer [Member]
Stock Compensation Plan disclosure [Abstract]
Grant date fair value of shares issued (in dollars per share) | $ / shares			$ 142.89	$ 141.63	[7]
Restricted stock activity [Abstract]
Granted (in dollars per share) | $ / shares			$ 142.89	$ 141.63	[7]
Share Based Payment Arrangement [Abstract]
Grant date			Feb. 17, 2021	Feb. 13, 2020	[7]
Performance period		1/1/21 - 12/31/21	1/1/20 - 12/31/20	1/1/19 - 12/31/19	[7]
Range of earnable shares - low end of range		0	0	0	[7]
Range of earnable shares - high end of range		4,756	4,812	6,394	[7]
Shares determined			4,156	5,860	[7]
Shares determined	[8]	N/A (2)
Grant date	[8]	N/A (2)
Grant date		N/A (2)
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Individual performance awards [Member] | Executive Officer [Member] | End of the one-year performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		34.00%
Share Based Payment Arrangement [Abstract]
Vesting period		1 year
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Individual performance awards [Member] | Executive Officer [Member] | Following two years after performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		33.00%
Share Based Payment Arrangement [Abstract]
Vesting period		2 years
Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Service Condition Only Awards [Member] | Non Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		20.00%
Stock Compensation Plan disclosure [Abstract]
Share awards granted (in shares)		9,200	12,300	10,175
Grant date fair value of shares issued (in dollars per share) | $ / shares		$ 168.35	$ 105.30	$ 112.14
Restricted Stock Activity [Roll Forward]
Granted (in shares)		9,200	12,300	10,175
Restricted stock activity [Abstract]
Granted (in dollars per share) | $ / shares		$ 168.35	$ 105.30	$ 112.14
Share Based Payment Arrangement [Abstract]
Grant date		Jul. 07, 2021	May 06, 2020	May 14, 2019
Vesting period		5 years
Equity Incentive Plan 2013 [Member] | Award Recipient Type Employee [Member] | Restricted Stock [Member]
Share Based Payment Arrangement [Abstract]
Range of earnable shares - low end of range		0
Range of earnable shares - high end of range		118,911
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 Payment Arrangement [Abstract]
Number of years in total shareholder return performance period | Integer		4
New Director Stock Awards to be Issued in Future Periods [Member] | 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 Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting Rights (% vesting per year in future years)		25.00%
One year period [Member] | Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Individual performance awards [Member] | Executive Officer [Member] | End of the one-year performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage				20.00%
One year period [Member] | Equity Incentive Plan 2013 [Member] | Annual equity compensation awards | Individual performance awards [Member] | Executive Officer [Member] | Each of the following four years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage				20.00%
Share Based Payment Arrangement [Abstract]
Vesting period				4 years
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Restricted Stock [Member] | Service Condition Only Awards [Member] | Executive Officer [Member] | Rate for each of the following four years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		25.00%
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Long-term equity compensation awards | Executive Officer [Member]
Share Based Payment Arrangement [Abstract]
Valuation date		Feb. 25, 2021	Mar. 06, 2020	Mar. 07, 2019
Risk Free Interest Rate		0.39%	0.62%	2.52%
Expected Volatility Rate		30.51%	16.72%	18.13%
Expected Volatility Rate for Peer Group Companies, Minimum		26.87%	14.40%	14.27%
Expected Volatility Rate for Peer Group Companies, Maximum		54.25%	49.23%	35.76%
Expected Dividend Rate		2.27%	2.28%	2.72%
Number of simulation paths | Integer		1,000,000	1,000,000	1,000,000
Grant date fair value | $ / shares		$ 2,941,000	$ 2,037,000	$ 2,413,000
Vesting period		3 years
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Long-term equity compensation awards | Executive Officer [Member] | End of the three-year performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		75.00%
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Long-term equity compensation awards | Executive Officer [Member] | Following year after performance period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		25.00%
Three year period [Member] | Equity Incentive Plan 2013 [Member] | Long-term equity compensation awards | Shareholder Return Awards [Member] | Executive Officer [Member]
Share Based Payment Arrangement [Abstract]
Grant date		Feb. 25, 2021	Mar. 06, 2020	Mar. 07, 2019		Jun. 01, 2018
Performance period		1/1/21 - 12/31/23	1/1/20 - 12/31/22	1/1/19 - 12/31/21		1/1/18 - 12/31/20
Range of earnable shares - low end of range		0	0	0		0
Range of earnable shares - high end of range		36,400	25,261	33,442		27,086
Shares determined						27,086
Shares determined	[9]	N/A (1)	N/A (1)	N/A (1)

[1] Does not include the restricted shares that may be earned if the performance goals established in 2019 and 2020 for long-term performance and in 2021 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 118,911.

[2] Includes shares granted in prior years for which performance conditions have been satisfied and the number of shares have been determined

[3] The 2019 annual award vested 20% at the end of the one-year performance period and 20% in each of the following four years

[4] The 2019 annual award vested 20% at the end of the one-year performance period and 20% in each of the following four years

[5] The performance conditions for this award have not yet been satisfied and the number of shares have not yet been determined.

[6] The 2019 annual award had a separate component for the Company’s FFO per share for 2019.

[7] The 2019 annual award vested 20% at the end of the one-year performance period and 20% in each of the following four years

[8] The performance conditions for this award have not yet been satisfied and the grant date and number of shares have not yet been determined

[9] The performance conditions for this award have not yet been satisfied and the number of shares have not yet been determined.