Acquisitions and Joint Venture Investments - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 31, 2018 USD ($) Bed	Sep. 30, 2017 USD ($) Bed Property	Dec. 31, 2019 USD ($) Bed Property	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) land_parcel Bed Property	Mar. 31, 2020
Business Acquisition [Line Items]
Number of properties, under development | Property			2
Number of beds | Bed			112,800
Number of properties | Property			167
Cash paid for asset acquisitions			$ 8,559	$ 26,626	$ 375,541
In-process development properties
Business Acquisition [Line Items]
Number of properties | Property		3
Asset Acquisitions, Amount Expected To Be Invested		$ 524,900
The Edge - Stadium Centre | Owned Properties | Pre-Sale Arrangement
Business Acquisition [Line Items]
Number of beds | Bed	412
Asset acquisition, consideration transferred	$ 42,600
Payments to acquire land	10,000
Series of Individually Immaterial Asset Acquisitions
Business Acquisition [Line Items]
Number of beds | Bed					1,240
Asset acquisition, consideration transferred					$ 222,300
Number of properties | Property					3
Cash paid for asset acquisitions					$ 222,900
Core Transaction
Business Acquisition [Line Items]
Number of beds | Bed		3,776
Asset acquisition, consideration transferred		$ 306,000	$ 76,800		144,300
Number of student housing properties | Property		7
Limited partner ownership interest (percent)		100.00%
Number of properties		2	3
Number of operating properties purchased through joint venture arrangement | Property		2
Cash paid for asset acquisitions					146,100
Core Transaction | Scenario, Forecast
Business Acquisition [Line Items]
Number of properties						2
Land
Business Acquisition [Line Items]
Asset acquisition, consideration transferred	$ 16,600				12,000
Payments to acquire land					$ 8,900
Number of land parcels acquired | land_parcel					5
Asset acquisitions, fair value					$ 12,000
Land | In-process development properties
Business Acquisition [Line Items]
Asset acquisition, consideration transferred					$ 9,000
In-process development properties
Business Acquisition [Line Items]
Asset Acquisition, Pre-Sale Arrangement Purchase Price			$ 110,200
Number of beds | Bed			783
Payments to acquire land			$ 8,600
Repayment Of Mortgage and Construction Loans			$ 18,500