Schedule III Real Estate and Accumulated Depreciation - Part Two - Changes in Total Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Carrying amount of real estate investments [Roll Forward]
Gross real estate, beginning balance	$ 4,915,813	$ 4,685,336	$ 4,477,599
Acquisitions	265,129	142,255	122,448
Improvements	181,622	126,279	119,437
Properties held for sale	(49,973)	0	0
Dispositions and other	(39,114)	(38,057)	(34,148)
Gross real estate, ending balance	$ 5,273,477	$ 4,915,813	$ 4,685,336