Segment Reporting - Operating Activity Within Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 207,796	$ 230,534	$ 459,146	$ 454,720
Segment profit	138,639	158,514	310,969	311,696
Office Segment
Segment Reporting Information [Line Items]
Total revenues	176,989	202,189	396,878	399,479
Expenses	(60,301)	(64,308)	(129,965)	(127,757)
Segment profit	116,688	137,881	266,913	271,722
Multifamily Segment
Segment Reporting Information [Line Items]
Total revenues	30,807	28,345	62,268	55,241
Expenses	(8,856)	(7,712)	(18,212)	(15,267)
Segment profit	$ 21,951	$ 20,633	$ 44,056	$ 39,974