SCHEDULE II - 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 Receivables [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 260	$ 240	$ 735
Charged to expense	(57)	(93)	(1,844)
Charged to other accounts	11	0	0
Deductions	(89)	113	1,349
Balance at end of year	125	260	240
Inventory Valuation Reserves [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	2,383	2,643	4,535
Charged to expense	229	(224)	100
Charged to other accounts	556	0	0
Deductions	(24)	(36)	(1,992)
Balance at end of year	3,144	2,383	2,643
Inventory LIFO Reserves [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	28,776	29,961	32,926
Charged to expense	3,327	(1,185)	(2,965)
Charged to other accounts	0	0	0
Deductions	0	0	0
Balance at end of year	$ 32,103	$ 28,776	$ 29,961