Schedule II: Valuation and Qualifying accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 1,993	$ 2,219	$ 1,039
Additions: Charged Against Operations	705	348	1,304
Deductions: Uncollectible Accounts Written Off	(1,154)	(574)	(124)
Balance at End of Year	$ 1,544	$ 1,993	$ 2,219