Investments in Real Estate - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Asset Acquisition
Land	$ 100,922
Building and improvements	2,358,771
In place leases	190,020
Below market leases	(27,849)
Above market leases	12,180
Below market leasehold interests	54,252
Above market leasehold interests	(8,978)
Above market debt	0
Interest rate swaps	0
Net assets acquired	2,679,318
Other, net	60,913
Aggregate purchase price	$ 2,740,231
Business Combination
Land		$ 85,017	$ 19,828
Building and improvements		559,930	246,911
In place leases		56,807	24,646
Below market leases		(13,792)	(8,360)
Above market leases		4,626	1,336
Below market leasehold interests		4,189	2,698
Above market leasehold interests		(50)	(7,725)
Above market debt		(83)	0
Interest rate swaps		(779)	0
Net assets acquired		695,865	279,334
Other, net		4,899	1,526
Aggregate purchase price		$ 700,764	$ 280,860