Derivatives - Foreign Currency Forward Contracts (Details) In Thousands, unless otherwise specified	12 Months Ended			0 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Nov. 30, 2012 30 Day Forward Contract EURO [Member] EUR (€)	Nov. 30, 2011 30 Day Forward Contract EURO [Member] EUR (€)	Nov. 30, 2012 30 Day Forward Contract GBP [Member] GBP (£)	Nov. 30, 2011 30 Day Forward Contract GBP [Member] GBP (£)
Derivatives, Fair Value [Line Items]
Forward Contract Term				30 days	30 days	30 days	30 days
Derivative, Notional Amount				€ 527	€ 12	£ 565	£ 328
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	$ (11)	$ 221	$ 126