Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) category	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Number of tenant and building improvement categories | category	2
Collectibility of Tenant Reimbursements
Loss Contingencies [Line Items]
Additional expense related to such tenant audits/disputes	$ 0.5	$ 0.3	$ 1.1
NonIncremental Capital Expenditures
Loss Contingencies [Line Items]
Period for commitments for funding non-incremental capital expenditures	3 years
Non-incremental and incremental capital expenditures for tenant improvements	$ 45.6
NonIncremental Capital Expenditures | Maximum
Loss Contingencies [Line Items]
Period for commitments for funding non-incremental capital expenditures	5 years
Incremental Capital Expenditures
Loss Contingencies [Line Items]
Non-incremental and incremental capital expenditures for tenant improvements	$ 32.6