Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	$ 949,720	$ 790,801
Available for sale securities unrealized gains	2,387	3,688
Available for sale securities unrealized losses	(24,297)	(13,535)
Available for sale, at fair value	927,810	780,954
Held to maturity securities amortized cost	10,415	12,541
Held to maturity securities unrealized gains	0	180
Held to Matruity securities unrealized losses	(99)	0
Held to maturity securities fair value	10,316	12,721
Total securities amortized cost	960,135	803,342
Total securities unrealized gains	2,387	3,868
Total securities unrealized losses	(24,396)	(13,535)
Total securities fair value	938,126	793,675
Available for sale securities amortized cost	949,720
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	246,708	161,479
Available for sale securities unrealized gains	442	0
Available for sale securities unrealized losses	(4,467)	(3,875)
Available for sale, at fair value	242,683	157,604
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	675,368	594,944
Available for sale securities unrealized gains	1,943	3,671
Available for sale securities unrealized losses	(16,518)	(7,733)
Available for sale, at fair value	660,793	590,882
Held to maturity securities amortized cost	10,415	12,541
Held to maturity securities unrealized gains	0	180
Held to Matruity securities unrealized losses	(99)	0
Held to maturity securities fair value	10,316	12,721
Obligations of states and political subdivisions [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	935	2,355
Available for sale securities unrealized gains	2	4
Available for sale securities unrealized losses	0	0
Available for sale, at fair value	937	2,359
Individual name issuer trust preferred debt securities [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	13,307	18,106
Available for sale securities unrealized gains	0	0
Available for sale securities unrealized losses	(1,535)	(1,122)
Available for sale, at fair value	11,772	16,984
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	13,402	13,917
Available for sale securities unrealized gains	0	13
Available for sale securities unrealized losses	(1,777)	(805)
Available for sale, at fair value	$ 11,625	$ 13,125

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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