Securities (Held to Maturity Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 282,200	$ 284,587
Gross Unrealized Gains	14,226	13,793
Gross Unrealized Losses	(1,804)	(1,612)
Estimated Fair Value	294,622	296,768
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,482	5,734
Gross Unrealized Gains	178	217
Gross Unrealized Losses	(945)	(667)
Estimated Fair Value	4,715	5,284
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	276,718	278,853
Gross Unrealized Gains	14,048	13,576
Gross Unrealized Losses	(859)	(945)
Estimated Fair Value	$ 289,907	$ 291,484