Derivative Instruments (Current Period Cash Flow Hedges in AOCI (loss) before Taxes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments
Beginning Balance	$ 962	$ 2,462	$ 640
Net deferred losses on cash flow hedges for the period	(2,207)	1,415	(1,260)
Amount reclassified into current period earnings	101	85	(562)
Ending Balance	$ 3,068	$ 962	$ 2,462