Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	$ 544,595
Gross Unrealized Gains	10,861
Gross Unrealized Losses	(156)
Estimated Market Value	555,300
U.S. Federal agencies [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	455,175
Gross Unrealized Gains	4,512
Gross Unrealized Losses	(121)
Estimated Market Value	459,566
Mortgage backed securities [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	23,869
Gross Unrealized Gains	843
Gross Unrealized Losses	(3)
Estimated Market Value	24,709
States and political subdivisions [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	57,540
Gross Unrealized Gains	3,008
Gross Unrealized Losses	(10)
Estimated Market Value	60,538
Other securities [Member]
Unrealized gains and losses and estimated market values of debt securities available for sale
Amortized Cost	8,011
Gross Unrealized Gains	2,498
Gross Unrealized Losses	(22)
Estimated Market Value	$ 10,487