Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance for doubtful accounts [Member]
Valuation and qualifying accounts
Balance at Beginning of Year	$ 1,884	$ 1,644	$ 2,081
Additions	1,142	948	1,211
Deductions, Recoveries & Other	(770)	(708)	(1,648)
Balance at Ending of Year	2,256	1,884	1,644
Tax valuation allowance [Member]
Valuation and qualifying accounts
Balance at Beginning of Year	7,335	6,073	3,378
Additions	8,831	3,213	3,649
Deductions, Recoveries & Other	(4,327)	(1,951)	(954)
Balance at Ending of Year	$ 11,839	$ 7,335	$ 6,073