Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale securities amortized cost basis	$ 756,781	$ 750,745
Available for sale securities unrealized gains	4,805	5,008
Available for sale securities unrealized losses	(12,100)	(15,841)
Available for sale, at fair value	749,486	739,912
Held to maturity securities	13,942	15,633
Held to maturity securities unrealized gains	289	287
Held to maturity securities unrealized losses	0	0
Held to maturity securities fair value	14,231	15,920
Total available for sale and held to maturity securities amortized cost	770,723	766,378
Total available for sale and held to maturity securities unrealized gains	5,094	5,295
Total available for sale and held to maturity securities unrealized losses	(12,100)	(15,841)
Total available for sale and held to maturity securities fair value	763,717	755,832
Obligations of U.S. government agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale securities amortized cost basis	131,484	111,483
Available for sale securities unrealized gains	4	7
Available for sale securities unrealized losses	(2,558)	(3,050)
Available for sale, at fair value	128,930	108,440
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 Maturty Securities [Line Items]
Available for sale securities amortized cost basis	587,814	592,833
Available for sale securities unrealized gains	4,763	4,923
Available for sale securities unrealized losses	(7,928)	(9,671)
Available for sale, at fair value	584,649	588,085
Held to maturity securities	13,942	15,633
Held to maturity securities unrealized gains	289	287
Held to maturity securities unrealized losses	0	0
Held to maturity securities fair value	14,231	15,920
Obligations of states and political subdivisions [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale securities amortized cost basis	5,468	14,423
Available for sale securities unrealized gains	16	62
Available for sale securities unrealized losses	0	0
Available for sale, at fair value	5,484	14,485
Individual name issuer trust preferred debt securities
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale securities amortized cost basis	27,888	29,851
Available for sale securities unrealized gains	0	0
Available for sale securities unrealized losses	(1,498)	(3,115)
Available for sale, at fair value	26,390	26,736
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale securities amortized cost basis	4,127	2,155
Available for sale securities unrealized gains	22	16
Available for sale securities unrealized losses	(116)	(5)
Available for sale, at fair value	$ 4,033	$ 2,166

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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