Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest income / (expense), net	$ 792	$ 1,202	$ (197)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest income / (expense), net	$ 600	$ 400	$ 100