Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Sep. 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	$ 882,865	$ 949,720
Available for sale debt securities unrealized gains	9,573	2,387
Available for sale debt securities unrealized losses	(5,418)	(24,297)
Available for sale debt securities, at fair value	887,020	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	882,865	960,135
Total securities unrealized gains	9,573	2,387
Total securities unrealized losses	(5,418)	(24,396)
Total securities fair value	887,020	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	196,734	246,708
Available for sale debt securities unrealized gains	927	442
Available for sale debt securities unrealized losses	(337)	(4,467)
Available for sale debt securities, at fair value	197,324	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	659,096	675,368
Available for sale debt securities unrealized gains	8,614	1,943
Available for sale debt securities unrealized losses	(2,805)	(16,518)
Available for sale debt securities, at fair value	664,905	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	0	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	0	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	13,320	13,307
Available for sale debt securities unrealized gains	0	0
Available for sale debt securities unrealized losses	(899)	(1,535)
Available for sale debt securities, at fair value	12,421	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	13,715	13,402
Available for sale debt securities unrealized gains	32	0
Available for sale debt securities unrealized losses	(1,377)	(1,777)
Available for sale debt securities, at fair value	$ 12,370	$ 11,625

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

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