Securities (Held to maturity securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 284,030us-gaap_HeldToMaturitySecurities	$ 284,587us-gaap_HeldToMaturitySecurities
Gross Unrealized Gains	15,226	13,793
Gross Unrealized Losses	(1,596)	(1,612)
Estimated Fair Value	297,660	296,768
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,665	5,734
Gross Unrealized Gains	213	217
Gross Unrealized Losses	(754)	(667)
Estimated Fair Value	5,124	5,284
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	278,365	278,853
Gross Unrealized Gains	15,013	13,576
Gross Unrealized Losses	(842)	(945)
Estimated Fair Value	$ 292,536	$ 291,484

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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