Selected Financial Statement Information 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]
Valuation and Qualifying Accounts Disclosure [Line Items]
Opening balance	$ 46	$ 76	$ 84
Additional charged to costs and expenses	7	20	54
Write-offs	0	(50)	(62)
Ending balance	$ 53	$ 46	$ 76