Schedule II: Valuation and Qualifying 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 [Roll Forward]
Balance at Beginning of Year	$ 1,544	$ 1,993	$ 2,219
Additions: Charged Against Operations	(314)	705	348
Deductions: Uncollectible Accounts Written Off	(312)	(1,154)	(574)
Balance at End of Year	$ 918	$ 1,544	$ 1,993