Related Person Transactions - Narrative (Details) - Two North Riverside Plaza Joint Venture Limited Partnership $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) option	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) option	Sep. 30, 2018 USD ($)
Related Party Transaction [Line Items]
Lease term	5 years		5 years
Number of renewal options of lease arrangement | option	1		1
Renewal term of lease arrangement	5 years		5 years
Tenant improvements	$ 0.7		$ 0.7
Lease termination period term			30 days
Operating lease, expense	$ 0.2	$ 0.2	$ 0.7	$ 0.6