Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ground_lease	Jun. 30, 2019 USD ($)
Long-term Purchase Commitment [Line Items]
Commitments for contracts and executed leases, operating and redevelopment and development properties	$ 814.8		$ 814.8
Weighted average discount rate, ground leases	5.11%		5.11%
Weighted average remaining lease term	55 years		55 years
Variable lease, cost	$ 0.9	$ 0.8	$ 1.7	$ 1.5
Environmental matters [Member]
Long-term Purchase Commitment [Line Items]
Accrued environmental remediation liabilities	$ 61.9		$ 61.9
Ten year ground lease extension option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | ground_lease			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 | ground_lease			1
Ground lease extension option term			45 years