Commitments and Contingencies (Details 1) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Extensions	Dec. 31, 2013 USD ($)	Dec. 31, 2014 USD ($)
Long-term Purchase Commitment [Line Items]
Commitments for contracts and executed leases, operating and redevelopment and development properties	$ 430.1
Period after which Ground lease rentals are adjusted based on fair market value and the Consumer Price Index	5 years
Annual ground lease rental obligations limit	$ 1.0
Duration of ground lease prior to increase	5 years
Average annual precentage rent for previous five years (percent)	50.00%
Accrued environmental remediation liabilities	$ 20.9		$ 15.5
Ten Year Ground Lease Extension Option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | Extensions	3
Ground lease extension option term	10 years
Forty-Five Year Ground Lease Extension Option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | Extensions	1
Ground lease extension option term	45 years
Property Damage Litigation Case [Member]
Long-term Purchase Commitment [Line Items]
Proceeds from Legal Settlements		$ 5.2
Former Tenant Litigation Case [Member]
Long-term Purchase Commitment [Line Items]
Proceeds from Legal Settlements		$ 3.7