Real Estate Pro Forma Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended								8 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real Estate [Line Items]
Total revenue	$ 81,746	$ 82,339	$ 77,106	$ 73,792	$ 76,562	$ 75,976	$ 71,819	$ 70,731	$ 12,650	$ 314,983	$ 295,088	$ 275,623
Operating Expenses									16,320	221,337	197,147	181,472
Operating income (loss)	23,792	26,477	20,048	23,329	25,110	25,484	23,704	23,643	(3,670)	93,646	97,941	94,151
Net income	$ 9,731	$ 12,505	$ 7,588	$ 10,308	$ 12,408	$ 11,858	$ 10,650	$ 10,721	$ (3,670)	40,132	45,637	$ 53,915
Pro Forma
Real Estate [Line Items]
Total revenue										322,050	312,414
Operating Expenses										230,796	215,631
Operating income (loss)										91,255	96,783
Net income										$ 36,433	$ 41,916