Investments (Fair Value and Gross Pre-Tax Net Unrealized Loss of Securities By Length of Time) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale Securities
AFS Fair Value, Less than 12 Months	$ 559,701	$ 516,259
AFS Unrealized Losses, Less than 12 months	(17,078)	(3,379)
AFS Fair Value, 12 months or longer	169,246	230,770
AFS Unrealized Losses, 12 months or longer	(7,337)	(4,359)
AFS Fair Value	728,947	747,029
AFS Unrealized Losses	(24,415)	(7,738)
Available-for-sale Securities \| U.S. Government and Government Agencies [Member]
AFS Fair Value, Less than 12 Months	4,855
AFS Unrealized Losses, Less than 12 months	(46)
AFS Fair Value, 12 months or longer	0
AFS Unrealized Losses, 12 months or longer	0
AFS Fair Value	4,855
AFS Unrealized Losses	(46)
Available-for-sale Securities \| Foreign Government [Member]
AFS Fair Value, Less than 12 Months		1,416
AFS Unrealized Losses, Less than 12 months		(2)
AFS Fair Value, 12 months or longer		0
AFS Unrealized Losses, 12 months or longer		0
AFS Fair Value		1,416
AFS Unrealized Losses		(2)
Available-for-sale Securities \| Obligations of States and Political Subdivisions [Member]
AFS Fair Value, Less than 12 Months	15,929	35,838
AFS Unrealized Losses, Less than 12 months	(164)	(270)
AFS Fair Value, 12 months or longer	0	0
AFS Unrealized Losses, 12 months or longer	0	0
AFS Fair Value	15,929	35,838
AFS Unrealized Losses	(164)	(270)
Available-for-sale Securities \| Corporate Securities [Member]
AFS Fair Value, Less than 12 Months	100,989	84,832
AFS Unrealized Losses, Less than 12 months	(7,444)	(480)
AFS Fair Value, 12 months or longer	2,695	20,182
AFS Unrealized Losses, 12 months or longer	(358)	(830)
AFS Fair Value	103,684	105,014
AFS Unrealized Losses	(7,802)	(1,310)
Available-for-sale Securities \| Collateralized Loan Obligations and Other Asset Backed Securities [Member]
AFS Fair Value, Less than 12 Months	302,492	205,191
AFS Unrealized Losses, Less than 12 months	(7,804)	(1,938)
AFS Fair Value, 12 months or longer	149,893	204,385
AFS Unrealized Losses, 12 months or longer	(6,394)	(3,496)
AFS Fair Value	452,385	409,576
AFS Unrealized Losses	(14,198)	(5,434)
Available-for-sale Securities \| Residential Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 Months	55,128	126,089
AFS Unrealized Losses, Less than 12 months	(300)	(425)
AFS Fair Value, 12 months or longer	2,316	5,375
AFS Unrealized Losses, 12 months or longer	(33)	(30)
AFS Fair Value	57,444	131,464
AFS Unrealized Losses	(333)	(455)
Available-for-sale Securities \| Commercial Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 Months	80,308	62,893
AFS Unrealized Losses, Less than 12 months	(1,320)	(264)
AFS Fair Value, 12 months or longer	14,342	828
AFS Unrealized Losses, 12 months or longer	(552)	(3)
AFS Fair Value	94,650	63,721
AFS Unrealized Losses	(1,872)	(267)
Available-for-sale Securities [Member]
AFS Unrealized Losses	$ (24,400)	$ (7,700)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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