Investments in Real Estate - Summary of properties (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) university_system Property	Dec. 31, 2018 USD ($)
Real Estate Properties [Line Items]
Owned properties, net	$ 6,769,903	$ 6,661,034
Number of properties \| Property	167
Owned Properties
Real Estate Properties [Line Items]
Land	$ 654,985	653,522
Buildings and improvements	6,749,757	6,486,106
Furniture, fixtures and equipment	391,208	371,429
Construction in progress	341,554	302,902
Real estate properties gross	8,137,504	7,813,959
Less accumulated depreciation	(1,442,789)	(1,230,562)
Owned properties, net	6,694,715	6,583,397
On-campus participating properties, net
Real Estate Properties [Line Items]
Buildings and improvements	155,941	150,087
Furniture, fixtures and equipment	13,552	11,817
Construction in progress	6	658
Real estate properties gross	169,499	162,562
Less accumulated depreciation	(94,311)	(84,925)
Owned properties, net	$ 75,188	$ 77,637
Number of properties \| Property	6
Number of university systems \| university_system	3
Percentage of net cash flow receivable per agreement	50.00%

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This element represents number of systems.

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- Definition

Amount before accumulated depreciation of building structures held for productive use including addition, improvement, or renovation to the structure, including, but not limited to, interior masonry, interior flooring, electrical, and plumbing.

+ References

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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- Definition

Amount before accumulated depreciation of equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.

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Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

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The number of real estate properties owned as of the balance sheet date.

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Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Amount of accumulated depreciation for real estate owned (REO).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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