Loans Credit Quality Indicator (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 23,947,536	$ 24,451,724
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,909,119	7,701,422
Commercial real estate — owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	880,755	900,912
Commercial and business lending
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	9,195,355	9,370,091
Commercial real estate — investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,300,651	4,342,584
Real estate construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,880,897	1,840,417
Commercial real estate lending
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	6,181,549	6,183,001
Total commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	15,376,904	15,553,091
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,638,372	7,878,324
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	631,783	707,255
Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	300,477	313,054
Total consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 8,570,632	$ 8,898,632