Accounts payable, accrued expenses, and tenant security deposits (Details) $ in Thousands, ft² in Millions		3 Months Ended	6 Months Ended
	Apr. 01, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) ft²	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Accounts payable and accrued expenses			$ 282,440		$ 239,838
Acquired below market leases			23,963		26,018
Asset Retirement Obligation			3,714		5,777
Deferred Rent Liability			36,043		27,664
Derivative Liability			12,332		4,314
Prepaid Rent and Tenant Security Deposits			205,790		211,605
Other Accounts Payable and Accrued Liabilities			29,346		74,140
Accounts Payable and Accrued Liabilities			593,628		$ 589,356
Payable for purchase of noncontrolling interest			0	$ 52,672
Alexandria Technology Square [Member]
Payable for purchase of noncontrolling interest	$ 54,300	$ 108,300	$ 54,000
Alexandria Technology Square [Member]
Area of Real Estate Property | ft²			1.2