Loans Composition (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Loans	$ 25,003,753	$ 22,821,440
PPP
Loans and Leases Receivable Disclosure [Line Items]
Loans	1,022,217	0
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Loans	7,933,404	7,354,594
Commercial real estate — owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Loans	904,997	911,265
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Loans	9,860,618	8,265,858
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Loans	4,320,926	3,794,517
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Loans	1,859,609	1,420,900
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Loans	6,180,536	5,215,417
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	16,041,154	13,481,275
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Loans	7,885,523	8,136,980
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Loans	761,593	852,025
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans	315,483	351,159
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans	$ 8,962,599	$ 9,340,164