Fair Value of Financial Assets and Liabilities, Financial Impact of Qualifying Cash Flow Hedges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Financial Impact of Qualifying Cash Flow Hedges on Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive loss related to cash flow hedges at beginning of period	$ (1,247)	$ (1,418)	$ (1,332)	$ (1,504)
After-tax net realized losses on derivative transactions reclassified into earnings	44	43	129	129
Accumulated other comprehensive loss related to cash flow hedges at end of period	$ (1,203)	$ (1,375)	$ (1,203)	$ (1,375)