Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Financial Instruments
Sales	$ 103,102	$ 79,783	$ 79,355	$ 67,219	$ 90,560	$ 82,883	$ 86,320	$ 74,650	$ 329,459	$ 334,413	$ 341,573
Cost of goods sold									236,220	237,576	250,545
Unrealized gain (loss) on cash flow hedges | Amount reclassified from AOCI
Derivative Financial Instruments
Sales									(20)	200
Cost of goods sold										$ 700