Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	$ 895,273	$ 949,720
Available for sale securities unrealized gains	9,117	2,387
Available for sale securities unrealized losses	(4,900)	(24,297)
Available for sale debt securities, at fair value	899,490	927,810
Held to maturity securities, amortized cost	0	10,415
Held to maturity securities unrealized gains		0
Held to Matruity securities unrealized losses		(99)
Held to maturity securities, fair value	0	10,316
Total securities amortized cost	895,273	960,135
Total securities unrealized gains	9,117	2,387
Total securities unrealized losses	(4,900)	(24,396)
Total securities fair value	899,490	938,126
Available for sale securities amortized cost	895,273
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	157,255	246,708
Available for sale securities unrealized gains	626	442
Available for sale securities unrealized losses	(233)	(4,467)
Available for sale debt securities, at fair value	157,648	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 Maturity Securities [Line Items]
Available for sale securities amortized cost	713,553	675,368
Available for sale securities unrealized gains	8,491	1,943
Available for sale securities unrealized losses	(2,964)	(16,518)
Available for sale debt securities, at fair value	719,080	660,793
Held to maturity securities, amortized cost		10,415
Held to maturity securities unrealized gains		0
Held to Matruity securities unrealized losses		(99)
Held to maturity securities, fair value		10,316
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
Available for sale securities unrealized gains		2
Available for sale securities unrealized losses		0
Available for sale debt securities, at fair value		937
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	13,324	13,307
Available for sale securities unrealized gains	0	0
Available for sale securities unrealized losses	(745)	(1,535)
Available for sale debt securities, at fair value	12,579	11,772
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	11,141	13,402
Available for sale securities unrealized gains	0	0
Available for sale securities unrealized losses	(958)	(1,777)
Available for sale debt securities, at fair value	$ 10,183	$ 11,625

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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