Valuation and Qualifying Account - Allowance for Doubtful Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	$ 725	$ 763	$ 844
Credited to Costs and Expenses	100	0	0
Deductions	273	38	81
Balance at End of Period	552	725	763
Accounts written-off as uncollectible	$ 273	28	84
Net addition (reduction) to the allowance balance		$ (10)	$ 3