Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Additions Charged to Cost and Expenses	$ 3,613	$ 4,604	$ 13,289
Income tax provision	5,064	(859)	(9,601)
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	42	42	673
Additions Charged to Cost and Expenses	0	0	134
Deductions	(9)	0	(765)
Balance at End of Year	33	42	42
Deferred tax asset valuation allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	18,248	13,644	33,889
Additions Charged to Cost and Expenses	3,613	4,604	13,289
Deductions	0	0	(33,534)
Balance at End of Year	$ 21,861	$ 18,248	13,644
Valuation Allowance, Operating Loss Carryforwards
Movement in Valuation Allowances and Reserves [Roll Forward]
Income tax provision			$ 355