Segments - Schedule of Segment Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total revenues		$ 185,547	$ 217,371	$ 434,951	$ 459,502
Ground/facility lease expense		(2,893)	(3,236)	(6,962)	(6,785)
Interest expense, net		(27,168)	(27,068)	(54,951)	(54,129)
Depreciation and amortization		(66,441)	(68,815)	(132,610)	(137,570)
Operating expenses		(173,035)	(179,530)	(306,953)	(362,662)
Total consolidated revenues, including interest income		186,417	218,340	436,672	461,397
Segment income before depreciation and amortization		12,512	37,841	127,998	96,840
(Loss) gain from disposition of real estate		0	(282)	48,525	(282)
Provision for impairment		0	0	0	(3,201)
Loss from early extinguishment of debt	$ (4,800)	0	0	(4,827)	0
Income tax provision		(381)	(314)	(760)	(678)
Net (loss) income		(15,422)	10,210	66,639	41,578
Operating segments
Segment Reporting Information [Line Items]
Total revenues		185,669	217,560	435,209	459,851
Depreciation and amortization		(65,556)	(67,644)	(130,836)	(135,177)
Segment income before depreciation and amortization		84,612	109,917	223,848	242,281
Net (loss) income		(15,422)	10,210	66,639	41,578
Operating segments | Owned properties
Segment Reporting Information [Line Items]
Rental revenues and other income		177,488	203,903	410,299	429,104
Interest income		115	119	232	238
Total revenues		177,603	204,022	410,531	429,342
Operating expenses before depreciation, amortization, and ground/facility lease expense		(85,749)	(90,763)	(178,223)	(182,932)
Ground/facility lease expense		(2,639)	(2,408)	(5,848)	(5,075)
Interest expense, net		(3,057)	(4,014)	(6,103)	(8,777)
Operating (loss) income before depreciation and amortization		86,158	106,837	220,357	232,558
Depreciation and amortization		(63,511)	(65,628)	(126,754)	(131,132)
Capital expenditures		85,621	129,833	181,832	245,352
Operating segments | On-campus participating properties
Segment Reporting Information [Line Items]
Rental revenues and other income		4,101	6,396	14,810	17,844
Interest income		7	70	26	111
Total revenues		4,108	6,466	14,836	17,955
Operating expenses before depreciation, amortization, and ground/facility lease expense		(3,208)	(3,806)	(6,574)	(7,763)
Ground/facility lease expense		(254)	(828)	(1,114)	(1,710)
Interest expense, net		(1,173)	(1,311)	(2,315)	(2,614)
Operating (loss) income before depreciation and amortization		(527)	521	4,833	5,868
Depreciation and amortization		(2,045)	(2,016)	(4,082)	(4,045)
Capital expenditures		601	537	1,166	767
Operating segments | Development Services
Segment Reporting Information [Line Items]
Operating (loss) income before depreciation and amortization		(790)	1,622	(1,260)	2,493
Development and construction management fees		1,290	3,607	3,345	6,778
Operating expenses		(2,080)	(1,985)	(4,605)	(4,285)
Operating segments | Property Management Services
Segment Reporting Information [Line Items]
Operating (loss) income before depreciation and amortization		(229)	937	(82)	1,362
Operating expenses		(2,897)	(2,528)	(6,579)	(4,414)
Unallocated
Segment Reporting Information [Line Items]
Total revenues		748	780	1,463	1,546
Corporate depreciation		(885)	(1,171)	(1,774)	(2,393)
Operating expenses		(31,957)	(29,078)	(64,995)	(56,622)
Segment reconciling items
Segment Reporting Information [Line Items]
Amortization of deferred financing costs		(1,255)	(1,218)	(2,542)	(2,350)
Property management fees from external customers | Operating segments | Property Management Services
Segment Reporting Information [Line Items]
Total revenues		$ 2,668	$ 3,465	$ 6,497	$ 5,776