Revenues - Summary of Revenues (Details) - USD ($) $ 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
Disaggregation Of Revenue [Line Items]
Rental revenue									$ 734,477	$ 727,295	$ 683,490
Fee income:
Total fee income									22,744	18,629	24,212
Other income									11,959	13,037	11,265
Total fee and other income									34,703	31,666	35,477
Total revenues	$ 190,488	$ 198,317	$ 188,583	$ 191,792	$ 190,675	$ 192,596	$ 191,419	$ 184,271	769,180	758,961	718,967
Property Management Fees [Member]
Fee income:
Total fee income									6,852	6,163	6,336
Asset Management Fees [Member]
Fee income:
Total fee income									10,442	7,912	8,581
Acquisition, Disposition and Leasing Fee [Member]
Fee income:
Total fee income									3,435	3,160	7,770
Other Fee Income [Member]
Fee income:
Total fee income									$ 2,015	$ 1,394	$ 1,525