Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale debt securities amortized cost basis	$ 968,784	$ 949,720
Available for sale debt securities unrealized gains	7,752	2,387
Available for sale debt securities unrealized losses	(7,368)	(24,297)
Available for sale debt securities, at fair value	969,168	927,810
Held to maturity debt securities	0	10,415
Held to maturity debt securities unrealized gains		0
Held to maturity debt securities unrealized losses		(99)
Held to maturity debt securities, fair value	0	10,316
Total securities amortized cost	968,784	960,135
Total securities unrealized gains	7,752	2,387
Total securities unrealized losses	(7,368)	(24,396)
Total securities fair value	969,168	938,126
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale debt securities amortized cost basis	236,726	246,708
Available for sale debt securities unrealized gains	1,005	442
Available for sale debt securities unrealized losses	(304)	(4,467)
Available for sale debt securities, at fair value	237,427	242,683
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 debt securities amortized cost basis	704,940	675,368
Available for sale debt securities unrealized gains	6,722	1,943
Available for sale debt securities unrealized losses	(4,482)	(16,518)
Available for sale debt securities, at fair value	707,180	660,793
Held to maturity debt securities		10,415
Held to maturity debt securities unrealized gains		0
Held to maturity debt securities unrealized losses		(99)
Held to maturity debt securities, fair value		10,316
Obligations of states and political subdivisions [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale debt securities amortized cost basis	90	935
Available for sale debt securities unrealized gains	0	2
Available for sale debt securities unrealized losses	0	0
Available for sale debt securities, at fair value	90	937
Individual name issuer trust preferred debt securities
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale debt securities amortized cost basis	13,315	13,307
Available for sale debt securities unrealized gains	0	0
Available for sale debt securities unrealized losses	(1,014)	(1,535)
Available for sale debt securities, at fair value	12,301	11,772
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturty Securities [Line Items]
Available for sale debt securities amortized cost basis	13,713	13,402
Available for sale debt securities unrealized gains	25	0
Available for sale debt securities unrealized losses	(1,568)	(1,777)
Available for sale debt securities, at fair value	$ 12,170	$ 11,625

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

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