Allowance for Credit Losses (Summary of Activity In Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 225,141	$ 223,712
Provision for Loan, Lease, and Other Losses	28,355	11,750
Initial PCD allowance	1,193
Charge-offs	(14,261)	(10,154)
Recoveries	6,755	3,467
Ending balance	209,259	228,775
Increase (decrease) in allowance	$ 209,259	228,775
Forecast period (months)	24 months
Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ (37,924)
Increase (decrease) in allowance	(37,924)		$ (37,900)
Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	187,217
Increase (decrease) in allowance	187,217
Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	33,213	35,270
Provision for Loan, Lease, and Other Losses	51	2,119
Initial PCD allowance	0
Charge-offs	0	(44)
Recoveries	87	131
Ending balance	2,290	37,476
Increase (decrease) in allowance	2,290	37,476
Commercial | Construction and land development | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(31,061)
Increase (decrease) in allowance	(31,061)
Commercial | Construction and land development | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,152
Increase (decrease) in allowance	2,152
Commercial | Owner occupied commercial mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	36,444
Provision for Loan, Lease, and Other Losses	6,107
Initial PCD allowance	0
Charge-offs	(320)
Recoveries	55
Ending balance	22,970
Increase (decrease) in allowance	22,970
Commercial | Owner occupied commercial mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(19,316)
Increase (decrease) in allowance	(19,316)
Commercial | Owner occupied commercial mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	17,128
Increase (decrease) in allowance	17,128
Commercial | Non-owner occupied commercial mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	11,102
Provision for Loan, Lease, and Other Losses	4,956
Initial PCD allowance	0
Charge-offs	0
Recoveries	13
Ending balance	16,531
Increase (decrease) in allowance	16,531
Commercial | Non-owner occupied commercial mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	460
Increase (decrease) in allowance	460
Commercial | Non-owner occupied commercial mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	11,562
Increase (decrease) in allowance	11,562
Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	61,610	55,620
Provision for Loan, Lease, and Other Losses	10,423	2,725
Initial PCD allowance	0
Charge-offs	(5,049)	(1,858)
Recoveries	1,272	538
Ending balance	30,619	57,025
Increase (decrease) in allowance	30,619	57,025
Commercial | Commercial and industrial | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(37,637)
Increase (decrease) in allowance	(37,637)
Commercial | Commercial and industrial | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	23,973
Increase (decrease) in allowance	23,973
Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		43,451
Provision for Loan, Lease, and Other Losses		2,371
Charge-offs		(761)
Recoveries		220
Ending balance		45,281
Increase (decrease) in allowance		45,281
Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		2,481
Provision for Loan, Lease, and Other Losses		(83)
Charge-offs		0
Recoveries		1
Ending balance		2,399
Increase (decrease) in allowance		2,399
Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		2,221
Provision for Loan, Lease, and Other Losses		(498)
Charge-offs		0
Recoveries		444
Ending balance		2,167
Increase (decrease) in allowance		2,167
Consumer | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,709	2,350
Provision for Loan, Lease, and Other Losses	(223)	123
Initial PCD allowance	0
Charge-offs	(70)	0
Recoveries	15	0
Ending balance	1,140	2,473
Increase (decrease) in allowance	1,140	2,473
Consumer | Construction and land development | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(1,291)
Increase (decrease) in allowance	(1,291)
Consumer | Construction and land development | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,418
Increase (decrease) in allowance	1,418
Consumer | Residential mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	18,232	15,472
Provision for Loan, Lease, and Other Losses	3,593	1,508
Initial PCD allowance	0
Charge-offs	(800)	(166)
Recoveries	223	173
Ending balance	38,366	16,987
Increase (decrease) in allowance	38,366	16,987
Consumer | Residential mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	17,118
Increase (decrease) in allowance	17,118
Consumer | Residential mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	35,350
Increase (decrease) in allowance	35,350
Consumer | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	19,702	21,862
Provision for Loan, Lease, and Other Losses	1,304	209
Initial PCD allowance	0
Charge-offs	(585)	(963)
Recoveries	471	387
Ending balance	24,557	21,495
Increase (decrease) in allowance	24,557	21,495
Consumer | Revolving mortgage | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,665
Increase (decrease) in allowance	3,665
Consumer | Revolving mortgage | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	23,367
Increase (decrease) in allowance	23,367
Consumer | Consumer auto
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,292
Provision for Loan, Lease, and Other Losses	958
Initial PCD allowance	0
Charge-offs	(944)
Recoveries	363
Ending balance	5,769
Increase (decrease) in allowance	5,769
Consumer | Consumer auto | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,100
Increase (decrease) in allowance	1,100
Consumer | Consumer auto | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	5,392
Increase (decrease) in allowance	5,392
Consumer | Consumer other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	30,301
Provision for Loan, Lease, and Other Losses	3,774
Initial PCD allowance	0
Charge-offs	(5,370)
Recoveries	1,359
Ending balance	40,101
Increase (decrease) in allowance	40,101
Consumer | Consumer other | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	10,037
Increase (decrease) in allowance	10,037
Consumer | Consumer other | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	40,338
Increase (decrease) in allowance	40,338
Consumer | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		35,841
Provision for Loan, Lease, and Other Losses		3,440
Charge-offs		(6,362)
Recoveries		1,573
Ending balance		34,492
Increase (decrease) in allowance		34,492
Non-PCD Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	217,605
Increase (decrease) in allowance	217,605
Non-PCD Loans | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Increase (decrease) in allowance			(56,900)
Non-PCD Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	33,213
Increase (decrease) in allowance	33,213
Non-PCD Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	59,374
Increase (decrease) in allowance	59,374
Non-PCD Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	45,335
Increase (decrease) in allowance	45,335
Non-PCD Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,211
Increase (decrease) in allowance	2,211
Non-PCD Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,236
Increase (decrease) in allowance	2,236
Non-PCD Loans | Consumer | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,709
Increase (decrease) in allowance	2,709
Non-PCD Loans | Consumer | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	18,232
Increase (decrease) in allowance	18,232
Non-PCD Loans | Consumer | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	34,593
Increase (decrease) in allowance	34,593
PCD Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	7,536	9,144
Provision for Loan, Lease, and Other Losses	(2,588)	(164)
Initial PCD allowance	1,193
Charge-offs	(1,123)	0
Recoveries	2,897	0
Ending balance	26,916	8,980
Increase (decrease) in allowance	7,536	$ 8,980
PCD Loans | Adoption of ASC 326
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	19,001
Increase (decrease) in allowance	19,001		$ 19,000
PCD Loans | Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	26,537
Increase (decrease) in allowance	26,537
Novel Coronavirus (COVID-19)
Allowance for Loan and Lease Losses [Roll Forward]
Increase in ACL	$ 21,500