SCHEDULE III Real Estate and Accumulated Depreciation - Investment in Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]
Balance at beginning of year	$ 2,570,390	$ 2,529,641	$ 2,510,579
Acquisitions	814,765	0	0
Improvements	179,787	40,749	21,899
Disposals	(1,638)		(2,837)
Balance at end of year	$ 3,563,304	$ 2,570,390	$ 2,529,641