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Concentration of credit risk [Abstract]

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Limited Partnership Maximum Expiration Terms

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Represents the number of largest tenants.

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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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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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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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Amount of cost for defined contribution plan.

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The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

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Commitments and contingencies (Details) $ in Millions	12 Months Ended
Commitments and contingencies (Details) $ in Millions	Dec. 31, 2019 USD ($) Tenant Lease	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Concentration Risk [Line Items]
Discretionary profit sharing contributions subject to statutory limitations	$ 4.9	$ 4.1	$ 3.2
Concentration of credit risk
Number of leases held \| Lease	820
Number of client tenants \| Tenant	622
Commitments
Remaining aggregate costs under contracts, under terms of leases	$ 1,100.0
Letters of credit and performance obligations	11.1
Investment commitments	$ 229.5
Limited Partnership Maximum Expiration Terms	12 years
Weighted-average remaining liquidation term (in years)	5 years 6 months
Minimum
Commitments
Expected period of payment obligation	1 year
Maximum
Commitments
Expected period of payment obligation	3 years
Single Tenant \| Lessee Concentration
Concentration of credit risk
Number of Single Tenant Properties \| Tenant	135
Single Tenant Properties as Percentage of Total Properties	46.00%
Three Largest Tenants \| Lessee Concentration \| Annualized Base Rent
Concentration of credit risk
Number of largest tenants	3
Concentration risk, percentage	10.20%
First Largest Tenant \| Lessee Concentration \| Annualized Base Rent
Concentration of credit risk
Concentration risk, percentage	4.10%
Second Largest Tenant \| Lessee Concentration \| Annualized Base Rent
Concentration of credit risk
Concentration risk, percentage	3.10%
Third Largest Tenant \| Lessee Concentration \| Annualized Base Rent
Concentration of credit risk
Concentration risk, percentage	3.00%
Investments in privately held entities that report NAV
Commitments
Weighted-average remaining liquidation term (in years)	8 years 7 months 6 days