Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Accounts and Notes Receivable Allowance [Member]	Dec. 31, 2010 Accounts Receivable Allowance [Member]	Dec. 31, 2009 Accounts Receivable Allowance [Member]
Movement In Valuation Allowances And Reserves Roll Forward
Balance at Beginning of Period	$ 1,185	$ 3,674	$ 3,323
Charged to Costs and Expenses, Additions	(160)	(409)	517
Charged to Other Accounts, Additions	0
Uncollectible Accounts Written-off	442	2,080	166
Balance at End of Period	$ 583	$ 1,185	$ 3,674