SCHEDULE II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts
Balance at Beginning of Period	$ 1,952	$ 695	$ 476
Charged to (Reduction of) Costs and Expenses	(275)	1,321	1,085
Taken Against Allowance	(152)	(64)	(866)
Other (Deductions) Recoveries	0	0	0
Balance at End of Period	1,525	1,952	695
Valuation on Allowance for Deferred Tax Assets
Balance at Beginning of Period	6,388	6,202	7,691
Charged to (Reduction of) Costs and Expenses	2,366	186	(1,484)
Taken Against Allowance	0	0	0
Other (Deductions) Recoveries	0	0	(5)
Balance at End of Period	$ 8,754	$ 6,388	$ 6,202