Loans Composition (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Loans	$ 24,832,671	$ 22,821,440
PPP
Loans and Leases Receivable Disclosure [Line Items]
Loans	1,012,033	0
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Loans	7,968,709	7,354,594
Commercial real estate — owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Loans	914,385	911,265
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Loans	9,895,127	8,265,858
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Loans	4,174,125	3,794,517
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Loans	1,708,189	1,420,900
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Loans	5,882,314	5,215,417
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Loans	15,777,441	13,481,275
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Loans	7,933,518	8,136,980
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Loans	795,671	852,025
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans	326,040	351,159
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Loans	$ 9,055,230	$ 9,340,164