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Represents the standard deposit insurance coverage provided by the Federal Deposit Insurance Corporation.

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Represents the term of ground lease obligation.

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Represents the net book value of ground leases related to operating property.

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Represents the number of ground leases related to operating property expiring in 2036.

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Represents the number of land development parcels under the terms of ground leases.

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Represents the number of largest tenants.

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Represents the number of leases held by the entity.

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Represents the total number of properties leased by the entity.

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Represents the number of properties under the terms of ground leases.

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Represents the number of tenants.

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Represents the term of operating lease obligation, excluding possible extensions.

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Represents the expected period of payment obligation.

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Represents the remaining aggregate costs under contracts for the construction of properties undergoing development and redevelopment and generic life science laboratory infrastructure improvements contracts under the terms of leases.

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Represents the number of properties in the rentable square feet of the entity.

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Represents single-tenant properties as a percentage of total properties.

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Area of a real estate property.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Carrying value as of the balance sheet date of obligations incurred and payable for the acquisition of merchandise, materials, supplies and services pertaining to construction projects such as a housing development or factory expansion not classified as trade payables.

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Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

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The amount of the cost recognized during the period for defined contribution plans.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Carrying amount of land available for development.

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Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

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Commitments and contingencies (Details)	12 Months Ended
Commitments and contingencies (Details)	Dec. 31, 2015 USD ($) ft² Lease property Tenant Parcel	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Mar. 31, 2015 USD ($)
Concentration Risk [Line Items]
Discretionary profit sharing contributions subject to statutory limitations	$ 2,000,000	$ 1,800,000	$ 1,600,000
FDIC insurance coverage	250,000
Largest aggregate notional amount in effect at any single point	$ 250,000,000
Number of leases held \| Lease	568
Number of client tenants \| Tenant	425
Rentable Square Feet Properties Number \| property	199
Remaining aggregate costs under contracts, under terms of leases	$ 885,200,000
Construction Payable	$ 128,900,000
Area of Real Estate Property \| ft²	20,073,784
Letters of credit and performance obligations	$ 28,400,000
Land available for development	283,761,000	253,723,000
Operating Leases, Rent Expense, Net	$ 13,700,000	$ 13,400,000	$ 11,400,000
Number of properties under terms of ground leases \| property	28
Number of land development parcels under terms of ground leases \| Parcel	4
Term of operating lease obligation related to office leases	7 years
Number of ground leases related to operating property that expires in 2036 \| Lease	1
Net book value	$ 9,700,000
Single Tenant \| Lessee Concentration
Concentration Risk [Line Items]
Number of Single Tenant Properties \| Tenant	87
Single Tenant Properties as Percentage of Total Properties	44.00%
Three Largest Tenants \| Lessee Concentration \| Annualized Base Rent
Concentration Risk [Line Items]
Number of largest tenants \| Tenant	3
Concentration risk, percentage	13.90%
First Largest Tenant \| Lessee Concentration \| Annualized Base Rent
Concentration Risk [Line Items]
Concentration risk, percentage	5.10%
Second Largest Tenant \| Lessee Concentration \| Annualized Base Rent
Concentration Risk [Line Items]
Concentration risk, percentage	4.80%
Third Largest Tenant \| Lessee Concentration \| Annualized Base Rent
Concentration Risk [Line Items]
Concentration risk, percentage	4.00%
Minimum
Concentration Risk [Line Items]
Expected period of payment obligation	1 year
Term of ground lease obligation	40 years
Maximum
Concentration Risk [Line Items]
Expected period of payment obligation	3 years
Term of ground lease obligation	100 years
Funding Investments
Concentration Risk [Line Items]
Fund commitment on certain investments	$ 87,600,000
Project Development Agreements
Concentration Risk [Line Items]
Land available for development	$ 42,900,000
Project Development Agreement, 2016 Completion
Concentration Risk [Line Items]
Area of land that is under construction commitment obligations \| ft²	300,000
Project Development Agreement, 2017 Completion
Concentration Risk [Line Items]
Area of land that is under construction commitment obligations \| ft²	100,000
Project Development Agreement, 2018 Completion
Concentration Risk [Line Items]
Area of land that is under construction commitment obligations \| ft²	200,000
Minimum cost per square foot \| Project Development Agreements
Concentration Risk [Line Items]
Land available for development				$ 125
Maximum cost per square foot \| Project Development Agreements
Concentration Risk [Line Items]
Land available for development				175
Alexandria Real Estate Equities, Inc. \| 1455/1515 Third Street \| San Francisco Bay Area
Concentration Risk [Line Items]
Equity interest percentage (in percent)	51.00%
1455/1515 Third Street \| San Francisco Bay Area
Concentration Risk [Line Items]
Area of Real Estate Property \| ft²	422,980
1455/1515 Third Street \| San Francisco Bay Area \| Minimum cost per square foot
Concentration Risk [Line Items]
Land available for development				230
1455/1515 Third Street \| San Francisco Bay Area \| Maximum cost per square foot
Concentration Risk [Line Items]
Land available for development				$ 270