Allowance for Credit Losses (Non-Accrual Loans and Leases and Loans and Leases Past Due) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total past due	$ 108,408	$ 84,187
Nonaccrual	31,076	26,244
Current	21,639,883	21,085,253
Total	21,779,367	21,195,684	$ 20,422,666
Financing Receivable, Allowance For Non-Accrual Credit Losses	16,700
GNMA Loans past due by 90 days, but not yet repurchased	0
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Current		89,500
Total Non-Accrual Loans [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual	31,100
Greater Than 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	24,791	19,560
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	47,256	22,322
Greater than 90 Days and Accruing
Financing Receivable, Past Due [Line Items]
Total past due	36,361	42,305
Commercial Real Estate | Non-owner occupied term, net
Financing Receivable, Past Due [Line Items]
Total past due	23,338	121
Nonaccrual	3,809	2,920
Current	3,478,655	3,542,525
Total	3,505,802	3,545,566
Commercial Real Estate | Owner Occupied Term, net
Financing Receivable, Past Due [Line Items]
Total past due	493	1,446
Nonaccrual	5,984	4,600
Current	2,327,468	2,490,042
Total	2,333,945	2,496,088
Commercial Real Estate | Multifamily, net
Financing Receivable, Past Due [Line Items]
Total past due	215	0
Nonaccrual	0	0
Current	3,348,981	3,514,774
Total	3,349,196	3,514,774
Commercial Real Estate | Construction & Development, net
Financing Receivable, Past Due [Line Items]
Total past due	3,991	0
Nonaccrual	0	0
Current	824,487	678,740
Total	828,478	678,740
Commercial Real Estate | Residential Development, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Nonaccrual	0	0
Current	192,761	189,010
Total	192,761	189,010
Commercial Real Estate | Greater Than 30 to 59 Days Past Due | Non-owner occupied term, net
Financing Receivable, Past Due [Line Items]
Total past due	1,214	0
Commercial Real Estate | Greater Than 30 to 59 Days Past Due | Owner Occupied Term, net
Financing Receivable, Past Due [Line Items]
Total past due	182	975
Commercial Real Estate | Greater Than 30 to 59 Days Past Due | Multifamily, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial Real Estate | Greater Than 30 to 59 Days Past Due | Construction & Development, net
Financing Receivable, Past Due [Line Items]
Total past due	3,991	0
Commercial Real Estate | Greater Than 30 to 59 Days Past Due | Residential Development, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial Real Estate | 60 to 89 Days Past Due | Non-owner occupied term, net
Financing Receivable, Past Due [Line Items]
Total past due	21,309	0
Commercial Real Estate | 60 to 89 Days Past Due | Owner Occupied Term, net
Financing Receivable, Past Due [Line Items]
Total past due	103	470
Commercial Real Estate | 60 to 89 Days Past Due | Multifamily, net
Financing Receivable, Past Due [Line Items]
Total past due	215	0
Commercial Real Estate | 60 to 89 Days Past Due | Construction & Development, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial Real Estate | 60 to 89 Days Past Due | Residential Development, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial Real Estate | Greater than 90 Days and Accruing | Non-owner occupied term, net
Financing Receivable, Past Due [Line Items]
Total past due	815	121
Commercial Real Estate | Greater than 90 Days and Accruing | Owner Occupied Term, net
Financing Receivable, Past Due [Line Items]
Total past due	208	1
Commercial Real Estate | Greater than 90 Days and Accruing | Multifamily, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial Real Estate | Greater than 90 Days and Accruing | Construction & Development, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial Real Estate | Greater than 90 Days and Accruing | Residential Development, net
Financing Receivable, Past Due [Line Items]
Total past due	0	0
Commercial | Term, net
Financing Receivable, Past Due [Line Items]
Total past due	566	517
Nonaccrual	2,205	3,458
Current	4,021,696	2,228,842
Total	4,024,467	2,232,817
Commercial | LOC & Other, net
Financing Receivable, Past Due [Line Items]
Total past due	4,165	3,960
Nonaccrual	336	767
Current	858,259	1,207,666
Total	862,760	1,212,393
Commercial | Leases and Equipment Finance, net
Financing Receivable, Past Due [Line Items]
Total past due	37,258	24,947
Nonaccrual	18,742	14,499
Current	1,400,630	1,426,043
Total	1,456,630	1,465,489
Commercial | Greater Than 30 to 59 Days Past Due | Term, net
Financing Receivable, Past Due [Line Items]
Total past due	562	136
Commercial | Greater Than 30 to 59 Days Past Due | LOC & Other, net
Financing Receivable, Past Due [Line Items]
Total past due	1,491	3,548
Commercial | Greater Than 30 to 59 Days Past Due | Leases and Equipment Finance, net
Financing Receivable, Past Due [Line Items]
Total past due	14,242	10,685
Commercial | 60 to 89 Days Past Due | Term, net
Financing Receivable, Past Due [Line Items]
Total past due	0	381
Commercial | 60 to 89 Days Past Due | LOC & Other, net
Financing Receivable, Past Due [Line Items]
Total past due	2,667	376
Commercial | 60 to 89 Days Past Due | Leases and Equipment Finance, net
Financing Receivable, Past Due [Line Items]
Total past due	18,220	11,176
Commercial | Greater than 90 Days and Accruing | Term, net
Financing Receivable, Past Due [Line Items]
Total past due	4	0
Commercial | Greater than 90 Days and Accruing | LOC & Other, net
Financing Receivable, Past Due [Line Items]
Total past due	7	36
Commercial | Greater than 90 Days and Accruing | Leases and Equipment Finance, net
Financing Receivable, Past Due [Line Items]
Total past due	4,796	3,086
Residential | Mortgage, net
Financing Receivable, Past Due [Line Items]
Total past due	33,212	44,746
Nonaccrual	0	0
Current	3,838,694	4,170,678
Total	3,871,906	4,215,424
Residential | Home Equity Loans & Lines, net
Financing Receivable, Past Due [Line Items]
Total past due	3,851	4,844
Nonaccrual	0	0
Current	1,132,213	1,232,668
Total	1,136,064	1,237,512
Residential | Greater Than 30 to 59 Days Past Due | Mortgage, net
Financing Receivable, Past Due [Line Items]
Total past due	1,587	0
Residential | Greater Than 30 to 59 Days Past Due | Home Equity Loans & Lines, net
Financing Receivable, Past Due [Line Items]
Total past due	844	2,173
Residential | 60 to 89 Days Past Due | Mortgage, net
Financing Receivable, Past Due [Line Items]
Total past due	3,912	8,104
Residential | 60 to 89 Days Past Due | Home Equity Loans & Lines, net
Financing Receivable, Past Due [Line Items]
Total past due	544	867
Residential | Greater than 90 Days and Accruing | Mortgage, net
Financing Receivable, Past Due [Line Items]
Total past due	27,713	36,642
Residential | Greater than 90 Days and Accruing | Mortgage, net | GNMA
Financing Receivable, Past Due [Line Items]
GNMA Loans past due by 90 days, but not yet repurchased		4,300
Residential | Greater than 90 Days and Accruing | Home Equity Loans & Lines, net
Financing Receivable, Past Due [Line Items]
Total past due	2,463	1,804
Consumer & Other, Net
Financing Receivable, Past Due [Line Items]
Total past due	1,319	3,606
Nonaccrual	0	0
Current	216,039	404,265
Total	217,358	407,871
Consumer & Other, Net | Greater Than 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	678	2,043
Consumer & Other, Net | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total past due	286	948
Consumer & Other, Net | Greater than 90 Days and Accruing
Financing Receivable, Past Due [Line Items]
Total past due	$ 355	$ 615