SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details)	2 Months Ended	3 Months Ended							11 Months Ended	12 Months Ended		26 Months Ended
	Nov. 30, 2017 property $ / shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2016 $ / shares	Nov. 30, 2017 USD ($) property $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Feb. 28, 2017 $ / shares	Dec. 31, 2017 property	Dec. 21, 2017 $ / shares	Apr. 20, 2017 $ / shares	Dec. 09, 2016 $ / shares	Jan. 17, 2013
Real Estate Properties [Line Items]
Impairment of real estate \| $									$ 0	$ 0	$ 0
Amended Dividend Reinvestment Plan common stock price per share as percent of common stock price per share from the public offering																	95.00%
Updated primary offering price (in dollars per share)															$ 8.35	$ 9.35
Special distribution (in dollars per share)															1.00
Dividend reinvestment plan, purchase price per share (in dollars per share)															$ 7.93
Distributions declared per common share (in dollars per share)	$ 0.000	$ 0.137	$ 1.091	$ 0.160	$ 0.164	$ 0.164	$ 0.162	$ 0.160	$ 1.388	$ 0.650	$ 0.650
Distribution rate per share per day, declared (in dollars per share)										$ 0.00178082	$ 0.00178082	$ 0.00178082
Initial liquidation distribution per share (in dollars per share)														$ 4.05
Apartment Building
Real Estate Properties [Line Items]
Number of real estate properties \| property													4
Apartment Building \| Disposed of by Sale
Real Estate Properties [Line Items]
Number of real estate properties \| property	6								6
Apartment Building \| Held-for-sale
Real Estate Properties [Line Items]
Number of real estate properties \| property	5								5

KBS Legacy Partners Apartment REIT, Inc. 10-K