Derivative Financial Instruments (Details 1) (Interest Rate Contracts One [Member], Derivative in cash flow hedging relationship [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
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	$ (170)	$ (1,951)	$ (589)	$ (2,268)