Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability derivatives	$ (93)	$ (976)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	0	0
Liability derivatives	0	0
Rabbi trust assets	1,922	1,494
Financial assets and financial liabilities, reported at fair value	1,922	1,494
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	847	304
Liability derivatives	(93)	(976)
Rabbi trust assets	0	0
Financial assets and financial liabilities, reported at fair value	754	(672)
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	0	0
Liability derivatives	0	0
Rabbi trust assets	0	0
Financial assets and financial liabilities, reported at fair value	0	0
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	847	304
Liability derivatives	(93)	(976)
Rabbi trust assets	1,922	1,494
Financial assets and financial liabilities, reported at fair value	$ 2,676	$ 822