Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finance Lease - Allowance for doubtful accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 527	$ 526	$ 526
Additions		1	0
(Reversals)	(527)
(Write-offs)/ Reversals	0	0	0
Ending Balance	0	527	526
Accounts Receivable-Allowance for doubtful accounts:
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	28,082	8,297	9,576
Additions	581	19,811
(Reversals)			(1,211)
(Write-offs)/ Reversals	(25,661)	(26)	(68)
Ending Balance	$ 3,002	$ 28,082	$ 8,297