Schedule III (Consolidated) - Real Estate and Accumulated Depreciation - Reconciliation of Real Estate Owned (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule III, Reconciliation of real estate owned
Balance at beginning of the year	$ 404,376	$ 381,969	$ 377,668
Amounts capitalized	43,306	39,261	13,875
Impairments	(99)	(714)	(357)
Cost of real estate sold	(18,928)	(14,274)	(6,489)
Amounts retired or adjusted	(10,161)	(1,866)	(2,728)
Balance at the end of the year	$ 418,494	$ 404,376	$ 381,969