Condensed Consolidated Statements of Changes in Equity (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019
Statement Of Stockholders Equity [Abstract]
Net loss allocated to redeemable non-controlling interest	$ 74	$ 277	$ 275	$ 347	$ 351
Distributions declared on common stock per share	$ 0.1588	$ 0.1582	$ 0.1566	$ 0.1552