Accounts payable, accrued expenses, and tenant security deposits (Notes)

12 Months Ended

Dec. 31, 2015

Accounts payable, accrued expenses, and tenant security deposits

The following table summarizes the components of accounts payable, accrued expenses, and tenant security deposits as of December 31, 2015 and 2014 (in thousands):



	December 31,
	2015		2014
Accounts payable and accrued expenses	$	239,838	$	218,938
Acquired below-market leases	26,018		8,810
Conditional asset retirement obligations	5,777		9,108
Deferred rent liabilities	27,664		36,231
Interest rate swap liabilities	4,314		909
Unearned rent and tenant security deposits	211,605		193,699
Other liabilities ⁽¹⁾	74,140		21,390
Total	$	589,356	$	489,085


(1)	Balance as of December 31, 2015, includes a $54.0 million liability related to the second installment payment due April 1, 2016, for our acquisition of the remaining noncontrolling interest in our 1.2 million RSF campus at Alexandria Technology Square^®.

Some of our properties may contain asbestos, which, under certain conditions, requires remediation. Although we believe that the asbestos is appropriately contained in accordance with environmental regulations, our practice is to remediate the asbestos upon the development or redevelopment of the affected property. 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, for certain properties, we have not recognized an asset retirement obligation when there is an indeterminate settlement date for the obligation because the period in which we may remediate the obligation may not be estimated with any level of precision to provide for a meaningful estimate of the retirement obligation. These conditional asset retirement obligations are included in the table above.