Loans Composition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	$ 24,365,633	$ 22,821,440
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	8,517,974	7,354,594
Commercial real estate — owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	940,687	911,265
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	9,458,661	8,265,858
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	4,038,036	3,794,517
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	1,544,858	1,420,900
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	5,582,894	5,215,417
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	15,041,555	13,481,275
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	8,132,417	8,136,980
Carrying Amount Of Loans Sold	200,000
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	844,901	852,025
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	346,761	351,159
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans(a)	$ 9,324,079	$ 9,340,164