Summary of Significant Accounting Policies - Recently Issued Accounting Standards (Details) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($) lease
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Real estate assets - operating lease right-of-use assets	$ 252,172	$ 264,643
Operating lease liabilities	$ 263,485	$ 274,783
Operating ground leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating ground leases | lease			22
Corporate facility leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating ground leases | lease			2
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Real estate assets - operating lease right-of-use assets			$ 104,863
Operating lease liabilities			$ 95,506