Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property Plant And Equipment [Line Items]
Capitalized internal leasing costs		$ 1,169,000	$ 1,491,000	$ 4,276,000	$ 4,488,000
Decrease in cash provided by used in operating activities continuing operations				134,168,000	102,071,000
Increase in cash provided by used in investing activities continuing operations				223,127,000	321,789,000
Adjustment to investments in unconsolidated joint ventures				$ 7,086,000
ASU 2016-18 [Member]
Property Plant And Equipment [Line Items]
Decrease in cash provided by used in operating activities continuing operations					(3,000,000)
Increase in cash provided by used in investing activities continuing operations					$ 5,946,000
ASU 2017-05 [Member] | RDF [Member] | One Steuart Lane [Member]
Property Plant And Equipment [Line Items]
Adjustment to investments in unconsolidated joint ventures	$ 7,086,000