Schedule-II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 19,865	$ 202
Additions Charged Against Operations	324	19,711
Uncollectible accounts Written-off	(19,596)	(48)
Balance at End of Year	593	19,865	$ 202
Allowance for Doubtful Accounts [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	277	202	365
Additions Charged Against Operations	324	123	315
Uncollectible accounts Written-off	(8)	(48)	(478)
Balance at End of Year	593	277	$ 202
Allowance for Preferred Equity Investments [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	19,588
Additions Charged Against Operations		19,588
Uncollectible accounts Written-off	$ (19,588)
Balance at End of Year		$ 19,588