Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	$ 513,392
Gross Unrealized Gains	10,517
Gross Unrealized Losses	(203)
Estimated Market Value	523,706
U.S. Federal agencies [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	429,163
Gross Unrealized Gains	4,126
Gross Unrealized Losses	(158)
Estimated Market Value	433,131
Mortgage backed securities [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	21,453
Gross Unrealized Gains	939
Gross Unrealized Losses	(2)
Estimated Market Value	22,390
States and political subdivisions [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	54,631
Gross Unrealized Gains	3,219
Gross Unrealized Losses	(21)
Estimated Market Value	57,829
Other securities [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	8,145
Gross Unrealized Gains	2,233
Gross Unrealized Losses	(22)
Estimated Market Value	$ 10,356