Derivative Financial Instruments (Derivatives not Designated as Hedging Instruments, Effect in Statements of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	$ 0	$ 0	$ 0	$ 0
Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	(787)	(836)	(869)	(1,269)
Commitments to originate fixed rate mortgage loans to be sold [Member] | Net gains on loan sales and commissions on loans originated for others [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	1,810	2,514	3,009	2,547
Commitments to sell fixed rate mortgage loans [Member] | Net gains on loan sales and commissions on loans originated for others [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	(2,660)	(3,304)	(3,965)	(3,810)
Interest rate swaps with customers [Member] | Net gains (losses) on interest rate swaps [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	340	1,373	949	2,491
Mirror swaps with counterparties [Member] | Net gains (losses) on interest rate swaps [Member] | Derivatives not Designated as Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	$ (277)	$ (1,419)	$ (862)	$ (2,497)