Loans, Loan Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 20,054,716	$ 18,714,343
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans	6,489,014	6,190,683
Commercial real estate — owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans	897,724	918,212
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans	7,386,738	7,108,895
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Total loans	3,574,732	3,234,266
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Total loans	1,432,497	1,162,145
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans	5,007,229	4,396,411
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans	12,393,967	11,505,306
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total loans	6,332,327	5,783,267
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Total loans	934,443	1,005,802
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans	393,979	419,968
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 7,660,749	$ 7,209,037