Derivative Instruments and Hedging Activities (Potential Impact of Rights of Offset Associated with Recognized Assets and Liabilities) (Details) (Hedging Contracts [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Current assets: Fair value of hedging contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 2,347
Derivative Asset, Collateral, Obligation to Return Cash, Offset	(836)
Derivative Asset, Fair Value, Amount Offset Against Collateral	1,511
Long-term assets: Fair value of hedging contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	286
Derivative Asset, Collateral, Obligation to Return Cash, Offset	(286)
Derivative Asset, Fair Value, Amount Offset Against Collateral	0
Current liabilities: Fair value of hedging contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(1,373)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	836
Derivative Liability, Fair Value, Amount Offset Against Collateral	537
Long-term liabilities: Fair value of hedging contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(617)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	286
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 331