Loans Credit Quality Indicator (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 24,162,328	$ 24,451,724
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,664,501	7,701,422
Commercial real estate — owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	883,237	900,912
Commercial and business lending
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	9,384,303	9,370,091
Commercial real estate — investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,260,706	4,342,584
Real estate construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,882,299	1,840,417
Commercial real estate lending
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	6,143,004	6,183,001
Total commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	15,527,307	15,553,091
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	7,685,218	7,878,324
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	651,647	707,255
Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	298,156	313,054
Total consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 8,635,020	$ 8,898,632