Summary of Quarterly Financial Data (Details) - 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
Quarterly Financial Information Disclosure [Abstract]
Revenues included in Discontinued Operations	$ 288,733	$ 282,276	$ 275,872	$ 286,257	$ 284,560	$ 278,310	$ 281,412	$ 276,693	$ 1,133,138	$ 1,120,975	$ 984,326
Net income attributable to common stockholders	40,291	56,965	51,728	90,446	78,904	69,722	47,841	52,660	$ 239,430	$ 249,127	$ 176,077
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Nonredeemable	178	157	109	190	167	147	100	111
Net income attributable to common unit holders	$ 40,469	$ 57,122	$ 51,837	$ 90,636	$ 79,071	$ 69,869	$ 47,941	$ 52,771
Income per common share - basic (note 15)	$ 0.24	$ 0.34	$ 0.31	$ 0.54	$ 0.47	$ 0.41	$ 0.28	$ 0.31	$ 1.43	$ 1.47	$ 1.00
Income per common share - diluted (note 15)	$ 0.24	$ 0.34	$ 0.31	$ 0.54	$ 0.46	$ 0.41	$ 0.28	$ 0.31	$ 1.43	$ 1.46	$ 1.00