SHAREHOLDERS' EQUITY - Distributions Table (Detail) - Cash Distributions - 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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Stockholders' Equity [Line Items]
Declared per Common Share (in dollars per share)	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.57	$ 0.57	$ 0.57
Paid in Cash	$ 23,268	$ 23,266	$ 11,641	$ 11,490	$ 11,433	$ 11,350	$ 11,262	$ 11,092	$ 10,923	$ 10,820	$ 10,349	$ 9,902	$ 69,665	$ 45,137	$ 41,994
Reinvested in Shares	0	0	11,601	11,699	11,863	11,897	11,980	12,086	12,222	12,242	11,868	11,447	23,300	47,826	47,779
Distributions Fees	2,071	2,070	2,052	2,033	1,900	1,880	1,864	1,845	1,781	1,764	1,630	1,495	8,226	7,489	6,670
Gross Distributions	$ 25,339	$ 25,336	$ 25,294	$ 25,222	$ 25,196	$ 25,127	$ 25,106	$ 25,023	$ 24,926	$ 24,826	$ 23,847	$ 22,844	$ 101,191	$ 100,452	$ 96,443