Commitments and Contingencies (Details)	1 Months Ended		3 Months Ended
	Mar. 31, 2020 USD ($) Property	Aug. 31, 2013 USD ($) extension	Mar. 31, 2020 USD ($) Property	Dec. 31, 2019 USD ($)
Loss Contingencies [Line Items]
Number of properties, under development | Property	3		3
Deferred pre-development costs	$ 9,500,000		$ 9,500,000
Litigation settlement	1,500,000
Litigation expense			$ 1,100,000	$ 400,000
Alternate Housing Guarantees
Loss Contingencies [Line Items]
Guarantee expiration period			5 days
Project Cost Guarantees
Loss Contingencies [Line Items]
Guarantee expiration period			1 year
Third-Party Development Projects
Loss Contingencies [Line Items]
Commitment under third-party development project	10,600,000		$ 10,600,000
Performance Guarantee
Loss Contingencies [Line Items]
Guarantee expiration period			60 days
Estimate of possible loss	614,600,000		$ 614,600,000
Earnest money deposits	2,100,000		2,100,000
Purchase and sale agreement upon exercise of option			28,700,000
Drexel University Property
Loss Contingencies [Line Items]
Lease term		40 years
Number of lease renewal options | extension		3
Lease extension period		10 years
Commitment to pay real estate transfer taxes, amount (not more than)			1,800,000
Real estate transfer taxes paid upon conveyance of land		$ 600,000
Drexel University Property | Maximum
Loss Contingencies [Line Items]
Commitment to pay real estate transfer taxes, amount (not more than)		$ 2,400,000
Disney College Program Phases I-V (ACE) | Performance Guarantee
Loss Contingencies [Line Items]
Development guarantee, damages due per bed each day of a delay			20
Guarantor obligations, maximum exposure	200,000		200,000
Construction Contracts
Loss Contingencies [Line Items]
Development projects under construction	$ 355,300,000		$ 355,300,000