Derivative Financial Instruments (Details 1) (Interest Rate Contracts One [Member], Derivative in cash flow hedging relationship [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Interest Rate Contracts One [Member] | Derivative in cash flow hedging relationship [Member]
Effect of the derivative instruments on the consolidated statement of income
Comprehensive Income on Derivative	$ (377)	$ (2,299)	$ (1,172)