Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 8	$ 129	$ 93
Charged to Costs and Expenses	0	132	123
Deductions	0	(253)	(87)
Balance at End of Period	8	8	129
Valuation allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	6,710	4,449	0
Charged to Costs and Expenses	7,063	2,261	4,449
Deductions	0	0	0
Balance at End of Period	$ 13,773	$ 6,710	$ 4,449