Segment Reporting - Operating Activity Within Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 216,987	$ 238,069	$ 676,133	$ 692,789
Segment profit	138,718	160,188	449,687	471,884
Office Segment
Segment Reporting Information [Line Items]
Total revenues	188,895	205,900	585,773	605,379
Expenses	(68,956)	(68,754)	(198,921)	(196,511)
Segment profit	119,939	137,146	386,852	408,868
Multifamily Segment
Segment Reporting Information [Line Items]
Total revenues	28,092	32,169	90,360	87,410
Expenses	(9,313)	(9,127)	(27,525)	(24,394)
Segment profit	$ 18,779	$ 23,042	$ 62,835	$ 63,016