Schedule III - Real Estate and Accumulated Depreciation - Accumulated Depreciation Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]
Accumulated depreciation, beginning of year	$ 1,391,368	$ 1,264,162	$ 1,139,853
Depreciation of real estate	211,893	198,578	190,515
Total additions during period	211,893	198,578	190,515
Write-offs due to sale	(41,655)	(71,372)	(66,206)
Properties held for sale	0	0	0
Other	(245)	0	0
Total deductions during period	(41,900)	(71,372)	(66,206)
Accumulated depreciation, end of year	$ 1,561,361	$ 1,391,368	$ 1,264,162