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SHAREHOLDERS' EQUITY - Narrative (Details) - USD ($)		3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
SHAREHOLDERS' EQUITY - Narrative (Details) - USD ($)	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity incentive plans
Dividends declared (in dollars per share)													$ 0.84	$ 0.80
Dividends paid (in dollars per share)		$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.84	$ 0.80
Restricted Shares
Compensation expense													$ 1,492,000	$ 995,000
Restricted Stock Units (RSUs)
Restricted Shares
Compensation expense													$ 142,000	$ (92,000)
Restricted stock
Restricted Shares
Grants in period (in shares)													156,399	144,797
Compensation expense													$ 1,350,000	$ 1,087,000
Unearned compensation					$ 2,735,000								$ 3,328,000	$ 2,735,000
Shares granted but not yet vested (in shares)					705,847								725,296	705,847	689,375
Vesting period for shares issued													5 years
Remaining weighted average vesting period													2 years 1 month 6 days
Restricted stock \| Subsequent Event
Restricted Shares
Grants in period (in shares)	158,299
Incentive Plan 2016
Restricted Shares
Shares authorized for issuance (in shares)													600,000
Incentive Plan 2016 \| Restricted Stock Units (RSUs)
Restricted Shares
Grants in period (in shares)													450,000
Recognized and unrecognized unearned compensation													$ 2,117,000
Recognized and unrecognized unearned compensation, reversed													1,432,000
General and administrative expense from unearned compensation													685,000
Compensation expense													142,000	$ (92,000)
Unearned compensation					$ 319,000								$ 177,000	$ 319,000
2012 Stock Incentive Plan
Restricted Shares
Shares authorized for issuance (in shares)													600,000
CAGR in Shareholder Return \| Incentive Plan 2016 \| Restricted Stock Units (RSUs)
Restricted Shares
Grants in period (in shares)													200,000
CAGR in Adjusted Funds from Operations \| Incentive Plan 2016 \| Restricted Stock Units (RSUs)
Restricted Shares
Grants in period (in shares)													200,000
CAGR Relative to FTSE NAREIT Equity Apartment Index \| Incentive Plan 2016 \| Restricted Stock Units (RSUs)
Restricted Shares
Grants in period (in shares)													50,000
Contingently issuable shares (in shares)													450,000
Contingently issuable shares, excluded from diluted earnings calculation (in shares)													250,000
Contingently issuable shares included in diluted earnings calculation (in shares)													200,000