Segment Reporting - Operating Activity Within Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 251,350	$ 224,186
Segment profit	172,330	153,182
Office Segment
Segment Reporting Information [Line Items]
Total revenues	219,889	197,290
Expenses	(69,664)	(63,449)
Segment profit	150,225	133,841
Multifamily Segment
Segment Reporting Information [Line Items]
Total revenues	31,461	26,896
Expenses	(9,356)	(7,555)
Segment profit	$ 22,105	$ 19,341