Derivatives Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended							6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Oct. 31, 2011 Cash Flow [Member] Interest Rate Swap [Member]	Sep. 30, 2011 Cash Flow [Member] Interest Rate Swap [Member]	Jun. 30, 2011 Cash Flow [Member] Interest Rate Swap [Member]	Jun. 30, 2011 Forward Commitments to Sell Mortgage Loans [Member]	Jun. 30, 2011 Interest Rate Swap [Member]	Jun. 30, 2011 Interest Expense [Member]
Interest rate swaps, Aggregate notional amount	$ 310,000,000		$ 310,000,000
Number of interest rate swaps	7		7
Amount reclassified from accumulated other comprehensive income to interest expense	2,197,000	2,199,000	4,369,000	4,392,000						6,700,000
Number of derivative transactions	314		314
Number customers in derivative transactions	157		157
Number of third parties in derivative transactions	157		157
Aggregate notional amount	239,600,000		239,600,000		75,000,000	60,000,000	310,000,000	318,100,000	891,700,000
Mortgage loans held-for-sale	139,000,000		139,000,000
Fair value of interest rate derivatives in a net liability position	29,500,000		29,500,000
Collateral securities	19,200,000		19,200,000
Cash collateral	$ 7,900,000		$ 7,900,000