Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for doubtful accounts
Activity in valuation and qualifying accounts
Balance at beginning of period	$ 160	$ 162	$ 162
Charged to costs and expenses			134
Other charges	(1)	(2)	(134)
Balance at end of period	159	160	162
Deferred tax assets valuation allowance
Activity in valuation and qualifying accounts
Balance at beginning of period	977	1,036	1,688
Charged to costs and expenses	(73)	(59)	(652)
Balance at end of period	$ 904	$ 977	$ 1,036