ACCOUNTING POLICIES - Revenue Recognition (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Revenue Recognition [Abstract]
Straight-line rent receivables	$ 262,028	$ 244,580
Straight-line rent receivables, allowance	$ 115,400	$ 109,800
Term of resident lease agreements, minimum	12 months
Term of resident lease agreements, maximum	18 months
Notice period to cancel lease agreements by the resident	30 days