Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reserve for Uncollectible Accounts:
Balance at Beginning of Period	$ 1,235	$ 1,358	$ 1,290
Charged to Costs and Expenses	173	322	373
Charged to Other Accounts	0	0	0
Deductions	(154)	(411)	(258)
Other	(14)	(34)	(47)
Balance at End of Period	$ 1,240	$ 1,235	$ 1,358