Real Estate and Lease Intangibles - Acquisitions and Dispositions - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) Building	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Building	Sep. 30, 2017 USD ($)
Net gain on sales of real estate properties	$ 114,672	$ 17,328	$ 256,834	$ 141,761
Net gain on sales of land parcels			995	$ 19,170
Non-cash asset impairment charge	$ 702		$ 702
San Francisco
Number of buildings damaged due to fire | Building	1		1