Allowance for Credit Losses (Summary of Activity In Allowance for Loan and Lease Losses) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jan. 01, 2020
Receivables [Abstract]
Expected credit losses on SBA-PPP loans					$ 0
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 209,259,000	$ 228,775,000	$ 225,141,000	$ 223,712,000
Provision (credits)	20,552,000	5,198,000	48,907,000	16,948,000
Initial PCD allowance			1,193,000
Charge-offs	(12,064,000)	(10,602,000)	(26,325,000)	(20,756,000)
Recoveries	4,703,000	3,212,000	11,458,000	6,679,000
Ending balance	222,450,000	226,583,000	222,450,000	226,583,000
Increase (decrease) in allowance	222,450,000	226,583,000	222,450,000	226,583,000	222,450,000
Decrease in allowance due to COVID-19			$ 36,100,000
Forecast period (years)			2 years
Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			$ (37,924,000)
Increase (decrease) in allowance			(37,924,000)			$ (37,900,000)
Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			187,217,000
Increase (decrease) in allowance			187,217,000
Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,290,000	37,476,000	33,213,000	35,270,000
Provision (credits)	4,705,000	(5,544,000)	4,756,000	(3,425,000)
Initial PCD allowance			0
Charge-offs	(138,000)	(28,000)	(138,000)	(72,000)
Recoveries	49,000	40,000	136,000	171,000
Ending balance	6,906,000	31,944,000	6,906,000	31,944,000
Increase (decrease) in allowance	6,906,000	31,944,000	33,213,000	31,944,000	6,906,000
Commercial | Construction and land development | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			(31,061,000)
Increase (decrease) in allowance			(31,061,000)
Commercial | Construction and land development | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			2,152,000
Increase (decrease) in allowance			2,152,000
Commercial | Owner occupied commercial mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	22,970,000		36,444,000
Provision (credits)	(721,000)		5,386,000
Initial PCD allowance			0
Charge-offs	0		(320,000)
Recoveries	240,000		295,000
Ending balance	22,489,000		22,489,000
Increase (decrease) in allowance	22,489,000		22,489,000		22,489,000
Commercial | Owner occupied commercial mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			(19,316,000)
Increase (decrease) in allowance			(19,316,000)
Commercial | Owner occupied commercial mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			17,128,000
Increase (decrease) in allowance			17,128,000
Commercial | Non-owner occupied commercial mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,531,000		11,102,000
Provision (credits)	5,542,000		10,498,000
Initial PCD allowance			0
Charge-offs	(8,000)		(8,000)
Recoveries	84,000		97,000
Ending balance	22,149,000		22,149,000
Increase (decrease) in allowance	22,149,000		11,102,000		22,149,000
Commercial | Non-owner occupied commercial mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			460,000
Increase (decrease) in allowance			460,000
Commercial | Non-owner occupied commercial mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			11,562,000
Increase (decrease) in allowance			11,562,000
Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	30,619,000	57,025,000	61,610,000	55,620,000
Provision (credits)	(2,898,000)	2,699,000	7,525,000	5,424,000
Initial PCD allowance			0
Charge-offs	(3,869,000)	(3,422,000)	(8,918,000)	(5,280,000)
Recoveries	781,000	599,000	2,053,000	1,137,000
Ending balance	24,633,000	56,901,000	24,633,000	56,901,000
Increase (decrease) in allowance	24,633,000	56,901,000	24,633,000	55,620,000	24,633,000
Commercial | Commercial and industrial | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			(37,637,000)
Increase (decrease) in allowance			(37,637,000)
Commercial | Commercial and industrial | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			23,973,000
Increase (decrease) in allowance			23,973,000
Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		45,281,000		43,451,000
Provision (credits)		3,714,000		6,085,000
Charge-offs		(89,000)		(850,000)
Recoveries		56,000		276,000
Ending balance		48,962,000		48,962,000
Increase (decrease) in allowance		48,962,000		48,962,000
Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		2,399,000		2,481,000
Provision (credits)		(57,000)		(140,000)
Charge-offs		0		0
Recoveries		0		1,000
Ending balance		2,342,000		2,342,000
Increase (decrease) in allowance		2,342,000		2,342,000
Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		2,167,000		2,221,000
Provision (credits)		(174,000)		(672,000)
Charge-offs		(31,000)		(31,000)
Recoveries		221,000		665,000
Ending balance		2,183,000		2,183,000
Increase (decrease) in allowance		2,183,000		2,221,000
Consumer | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,140,000	2,473,000	2,709,000	2,350,000
Provision (credits)	486,000	277,000	263,000	400,000
Initial PCD allowance			0
Charge-offs	0	0	(70,000)	0
Recoveries	14,000	0	29,000	0
Ending balance	1,640,000	2,750,000	1,640,000	2,750,000
Increase (decrease) in allowance	1,640,000	2,750,000	1,640,000	2,750,000	1,640,000
Consumer | Construction and land development | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			(1,291,000)
Increase (decrease) in allowance			(1,291,000)
Consumer | Construction and land development | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			1,418,000
Increase (decrease) in allowance			1,418,000
Consumer | Residential mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	38,366,000	16,987,000	18,232,000	15,472,000
Provision (credits)	4,909,000	371,000	8,502,000	1,879,000
Initial PCD allowance			0
Charge-offs	(460,000)	(478,000)	(1,260,000)	(644,000)
Recoveries	57,000	52,000	280,000	225,000
Ending balance	42,872,000	16,932,000	42,872,000	16,932,000
Increase (decrease) in allowance	42,872,000	16,932,000	42,872,000	15,472,000	42,872,000
Consumer | Residential mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			17,118,000
Increase (decrease) in allowance			17,118,000
Consumer | Residential mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			35,350,000
Increase (decrease) in allowance			35,350,000
Consumer | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	24,557,000	21,495,000	19,702,000	21,862,000
Provision (credits)	2,211,000	(328,000)	3,515,000	(119,000)
Initial PCD allowance			0
Charge-offs	(495,000)	(493,000)	(1,080,000)	(1,456,000)
Recoveries	367,000	447,000	838,000	834,000
Ending balance	26,640,000	21,121,000	26,640,000	21,121,000
Increase (decrease) in allowance	26,640,000	21,121,000	26,640,000	21,121,000	26,640,000
Consumer | Revolving mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			3,665,000
Increase (decrease) in allowance			3,665,000
Consumer | Revolving mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			23,367,000
Increase (decrease) in allowance			23,367,000
Consumer | Consumer auto
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	5,769,000		4,292,000
Provision (credits)	4,042,000		5,000,000
Initial PCD allowance			0
Charge-offs	(1,255,000)		(2,199,000)
Recoveries	342,000		705,000
Ending balance	8,898,000		8,898,000
Increase (decrease) in allowance	8,898,000		4,292,000		8,898,000
Consumer | Consumer auto | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			1,100,000
Increase (decrease) in allowance			1,100,000
Consumer | Consumer auto | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			5,392,000
Increase (decrease) in allowance			5,392,000
Consumer | Consumer other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	40,101,000		30,301,000
Provision (credits)	2,034,000		5,808,000
Initial PCD allowance			0
Charge-offs	(4,447,000)		(9,817,000)
Recoveries	1,607,000		2,966,000
Ending balance	39,295,000		39,295,000
Increase (decrease) in allowance	39,295,000		39,295,000		39,295,000
Consumer | Consumer other | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			10,037,000
Increase (decrease) in allowance			10,037,000
Consumer | Consumer other | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			40,338,000
Increase (decrease) in allowance			40,338,000
Consumer | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		34,492,000		35,841,000
Provision (credits)		4,877,000		8,317,000
Charge-offs		(6,061,000)		(12,423,000)
Recoveries		1,797,000		3,370,000
Ending balance		35,105,000		35,105,000
Increase (decrease) in allowance		35,105,000		35,105,000
Non-PCD Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			217,605,000
Increase (decrease) in allowance			217,605,000
Non-PCD Loans | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Increase (decrease) in allowance						(56,900,000)
Non-PCD Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			33,213,000
Increase (decrease) in allowance			33,213,000
Non-PCD Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			59,374,000
Increase (decrease) in allowance			59,374,000
Non-PCD Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			45,335,000
Increase (decrease) in allowance			45,335,000
Non-PCD Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			2,211,000
Increase (decrease) in allowance			2,211,000
Non-PCD Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			2,236,000
Increase (decrease) in allowance			2,236,000
Non-PCD Loans | Consumer | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			2,709,000
Increase (decrease) in allowance			2,709,000
Non-PCD Loans | Consumer | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			18,232,000
Increase (decrease) in allowance			18,232,000
Non-PCD Loans | Consumer | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			34,593,000
Increase (decrease) in allowance			34,593,000
PCD Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	26,916,000	8,980,000	7,536,000	9,144,000
Provision (credits)	242,000	(637,000)	(2,346,000)	(801,000)
Initial PCD allowance			1,193,000
Charge-offs	(1,392,000)	0	(2,515,000)	0
Recoveries	1,162,000	0	4,059,000	0
Ending balance	26,928,000	8,343,000	26,928,000	8,343,000
Increase (decrease) in allowance	$ 26,928,000	$ 8,343,000	7,536,000	$ 8,343,000	$ 26,928,000
PCD Loans | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			19,001,000
Increase (decrease) in allowance			19,001,000			$ 19,000,000.0
PCD Loans | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			26,537,000
Increase (decrease) in allowance			$ 26,537,000