Securities (Held to maturity securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 259,586	$ 263,662
Gross Unrealized Gains	14,541	12,282
Gross Unrealized Losses	(733)	(1,145)
Estimated Fair Value	273,394	274,799
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	259,586	263,662
Gross Unrealized Gains	14,541	12,282
Gross Unrealized Losses	(733)	(1,145)
Estimated Fair Value	$ 273,394	$ 274,799