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Fair Value Measurement, Number of Debt Securities

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Represents the number of properties acquired or agreed to be acquired by the entity.

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Value of input used to measure alternative investment.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Fair value portion of assets classified as held for sale.

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Fair value portion of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Fair Value of Assets and Liabilities - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) ft² property debt_security	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) property
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets	$ 66,346	$ 5,082	$ 18,674
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of debt securities \| debt_security	2
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of debt securities \| debt_security	5
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate held for sale	$ 1,928
Aggregate fair value of assets	11,167
Fair Value, Measurements, Nonrecurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate held for sale	0
Aggregate fair value of assets	0
Fair Value, Measurements, Nonrecurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate held for sale	1,928
Aggregate fair value of assets	$ 0
MOBs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of properties acquired or agreed to be acquired \| property	13		2
Impairment of assets	$ 46,797		$ 11,488
MOBs \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of properties acquired or agreed to be acquired \| property	11
Impairment of assets	$ 44,069
Aggregate fair value of assets	$ 11,167
MOBs \| Massachusetts \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of properties acquired or agreed to be acquired \| property	13
Discontinued Operations, Held-for-sale \| MOBs \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of properties acquired or agreed to be acquired \| property	2
Impairment of assets	$ 2,728
Real estate held for sale	$ 1,928
Discontinued Operations, Held-for-sale \| MOBs \| Massachusetts \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of properties acquired or agreed to be acquired \| property	2
Real Estate Properties \| Measurement Input, Estimated Market Rents \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input \| ft²	12.00
Real Estate Properties \| Measurement Input, Estimated Market Rents \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input \| ft²	16.00
Real Estate Properties \| Measurement Input, Estimated Market Rents \| Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input \| ft²	14.00
Real Estate Properties \| Measurement Input, Leasing And Capital Improvements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input \| ft²	40.00
Absorption time	18 months
Real Estate Properties \| Measurement Input, Cap Rate \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.09
Real Estate Properties \| Measurement Input, Cap Rate \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.10
Real Estate Properties \| Measurement Input, Cap Rate \| Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.08
Real Estate Properties \| Measurement Input, Discount Rate \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.10
Real Estate Properties \| Measurement Input, Discount Rate \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.11
Real Estate Properties \| Measurement Input, Discount Rate \| Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.09