Operating Leases (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) lease	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 20, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 01, 2019 USD ($)	Jan. 01, 2019 USD ($) lease
Lessee, Lease, Description [Line Items]
Lease income	$ 291,400,000
Lease income		$ 247,442,000	$ 257,465,000
Number of ground leases | lease	3						2
Weighted-average remaining lease term in years.	80 years 10 months 24 days
Lease liability	$ 45,020,000			$ 16,300,000		$ 600,000
Lease discount rate					$ 0.0394
Right of use asset	41,347,000			$ 16,300,000	$ 600,000
Operating lease cost	2,800,000
Operating lease payments	$ 1,200,000
Chicago Illinois Office
Lessee, Lease, Description [Line Items]
Weighted-average remaining lease term in years.	6 years
Right of use asset						$ 600,000
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Lease liability							$ 27,600,000
Right of use asset							$ 25,500,000