SUMMARY OF QUARTERLY RESULTS (UNAUDITED) (Detail) - USD ($) $ / shares in Units, $ 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
Summary Of Quarterly Results [Line Items]
Revenues	$ 246,668	$ 233,195	$ 225,279	$ 223,688	$ 219,750	$ 221,852	$ 219,881	$ 220,199	$ 928,830	$ 881,682	$ 908,385
Net income (loss)	61,146	142,948	75,671	72,182	64,903	59,062	81,986	87,933	351,947	293,884	104,910
Net income available to common stockholders	$ 59,540	$ 138,740	$ 73,141	$ 69,702	$ 62,216	$ 56,606	$ 78,536	$ 84,220	$ 341,123	$ 281,578	$ 100,419
Net income (loss) available to common per share:
Basic (in dollars per share)	$ 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
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
Omega OP
Summary Of Quarterly Results [Line Items]
Revenues	$ 246,668	$ 233,195	$ 225,279	$ 223,688	$ 219,750	$ 221,852	$ 219,881	$ 220,199	$ 928,830	$ 881,682	$ 908,385
Net income (loss)	61,146	142,948	75,671	72,182	64,903	59,062	81,986	87,933	351,947	293,884	104,910
Net income available to common stockholders	$ 61,149	$ 142,957	$ 75,671	$ 72,182	$ 64,903	$ 59,062	$ 81,986	$ 87,933	$ 351,959	$ 293,884	$ 104,910
Net income (loss) available to Omega OP Unit holders:
Basic (in dollars per share)	$ 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