Summary of Significant Accounting Policies - Components of rental income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Property operating income	$ 415,142	$ 390,256	$ 358,009
Single-tenant net lease	44,083	47,860	52,897
Straight-line rent	3,000	4,281	6,072
Rental income	$ 462,225
Rental income		$ 442,397	$ 416,978