Loans, Loan Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable [Line Items]
Loans	$ 24,451,724	$ 22,821,440
PPP
Loans and Leases Receivable [Line Items]
Loans	767,757	0
Commercial and industrial
Loans and Leases Receivable [Line Items]
Loans	7,701,422	7,354,594
Commercial real estate - owner occupied
Loans and Leases Receivable [Line Items]
Loans	900,912	911,265
Commercial and business lending
Loans and Leases Receivable [Line Items]
Loans	9,370,091	8,265,858
Commercial real estate - investor
Loans and Leases Receivable [Line Items]
Loans	4,342,584	3,794,517
Real estate construction
Loans and Leases Receivable [Line Items]
Loans	1,840,417	1,420,900
Commercial real estate lending
Loans and Leases Receivable [Line Items]
Loans	6,183,001	5,215,417
Total commercial
Loans and Leases Receivable [Line Items]
Loans	15,553,091	13,481,275
Residential mortgage
Loans and Leases Receivable [Line Items]
Loans	7,878,324	8,136,980
Home equity
Loans and Leases Receivable [Line Items]
Loans	707,255	852,025
Other consumer
Loans and Leases Receivable [Line Items]
Loans	313,054	351,159
Total consumer
Loans and Leases Receivable [Line Items]
Loans	$ 8,898,632	$ 9,340,164