Accounts payable, accrued expenses, and other liabilities (Notes)

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Accounts payable, accrued expenses, and tenant security deposits

The following table summarizes the components of accounts payable, accrued expenses, and other liabilities as of December 31, 2021 and 2020 (in thousands):

	December 31,
	2021		2020
Accounts payable and accrued expenses	$	513,416	$	285,021
Accrued construction	438,866		333,271
Acquired below-market leases	341,585		288,075
Conditional asset retirement obligations	59,797		47,070
Deferred rent liabilities	12,384		4,495
Operating lease liability	434,745		345,750
Unearned rent and tenant security deposits	326,924		276,751
Other liabilities	82,693		89,399
Total	$	2,210,410	$	1,669,832

As of December 31, 2021 and 2020, our conditional asset retirement obligations liability primarily consisted of the soil and groundwater remediation liabilities associated with certain of our properties. Some of our properties may contain asbestos or may be subjected to other hazardous or toxic substances, which, under certain conditions, requires remediation. We engage independent environmental consultants to conduct Phase I or similar environmental assessments at our properties. This type of assessment generally includes a site inspection, interviews, and a public records review, asbestos, lead-based paint and mold surveys, subsurface sampling, and other testing. We recognize a liability for the fair value of a conditional asset retirement obligation (including asbestos) when the fair value of the liability can be reasonably estimated. In addition, environmental laws and regulations subject our tenants, and potentially us, to liability that may result from our tenants’ routine handling of hazardous substances and wastes as part of their operations at our properties. These assessments and investigations of our properties have not to date revealed any additional environmental liability we believe would have a material adverse effect on our business and financial statements or that would require additional disclosures or recognition in our consolidated financial statements.