Schedule II: Valuation and Qualifying accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 1,039	$ 1,047	$ 1,736
Additions: Charged Against Operations	1,304	427	(22)
Deductions: Uncollectible Accounts Written Off	(124)	(435)	(667)
Balance at End of Year	$ 2,219	$ 1,039	$ 1,047