EARNINGS PER SHARE/UNIT (Schedule of Computation of Basic and Diluted Earnings per Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 61,146	$ 142,948	$ 75,671	$ 72,182	$ 64,903	$ 59,062	$ 81,986	$ 87,933	$ 351,947	$ 293,884	$ 104,910
(Less) Add: net income attributable to noncontrolling interests									(10,824)	(12,306)	(4,491)
Net income available to common stockholders/owners	$ 59,540	$ 138,740	$ 73,141	$ 69,702	$ 62,216	$ 56,606	$ 78,536	$ 84,220	$ 341,123	$ 281,578	$ 100,419
Denominator:
Denominator for basic earnings per share									213,404	200,279	197,738
Effect of dilutive securities:
Common stock equivalents									1,753	691	269
Net forward share contract									179
Noncontrolling interest - Omega OP Units									6,789	8,741	8,783
Denominator for diluted earnings per share									222,125	209,711	206,790
Earnings per share/unit - basic:
Net income available to common stockholders	$ 0.27	$ 0.64	$ 0.35	$ 0.34	$ 0.31	$ 0.28	$ 0.39	$ 0.42	$ 1.60	$ 1.41	$ 0.51
Net income (loss) per share
Net income	$ 0.27	$ 0.63	$ 0.34	$ 0.34	$ 0.31	$ 0.28	$ 0.39	$ 0.42	$ 1.58	$ 1.40	$ 0.51
Omega OP
Numerator:
Net income	$ 61,146	$ 142,948	$ 75,671	$ 72,182	$ 64,903	$ 59,062	$ 81,986	$ 87,933	$ 351,947	$ 293,884	$ 104,910
(Less) Add: net income attributable to noncontrolling interests									12
Net income available to common stockholders/owners	$ 61,149	$ 142,957	$ 75,671	$ 72,182	$ 64,903	$ 59,062	$ 81,986	$ 87,933	$ 351,959	$ 293,884	$ 104,910
Denominator:
Denominator for basic earnings per share									220,193	209,020	206,521
Denominator for basic earnings per unit									220,193	209,020	206,521
Effect of dilutive securities:
Common stock equivalents									1,753	691	269
Net forward share contract									179
Denominator for diluted earnings per share									222,125	209,711	206,790
Denominator for diluted earnings per unit									222,125	209,711	206,790
Earnings per share/unit - basic:
Net income available to owners'	$ 0.27	$ 0.64	$ 0.35	$ 0.34	$ 0.31	$ 0.28	$ 0.39	$ 0.42	$ 1.60	$ 1.41	$ 0.51
Net income (loss) per unit
Diluted (in dollars per share)	$ 0.27	$ 0.63	$ 0.34	$ 0.34	$ 0.31	$ 0.28	$ 0.39	$ 0.42	$ 1.58	$ 1.40	$ 0.51