Loans, Loan Composition (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 19,815,286	$ 18,714,343
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Total loans	6,701,986	6,190,683
Commercial real estate — owner occupied
Loans and Leases Receivable Disclosure [Line Items]
Total loans	921,736	918,212
Commercial and business lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans	7,623,722	7,108,895
Commercial real estate — investor
Loans and Leases Receivable Disclosure [Line Items]
Total loans	3,495,791	3,234,266
Real estate construction
Loans and Leases Receivable Disclosure [Line Items]
Total loans	1,285,573	1,162,145
Commercial real estate lending
Loans and Leases Receivable Disclosure [Line Items]
Total loans	4,781,364	4,396,411
Total commercial
Loans and Leases Receivable Disclosure [Line Items]
Total loans	12,405,086	11,505,306
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total loans	6,035,720	5,783,267
Home equity
Loans and Leases Receivable Disclosure [Line Items]
Total loans	968,771	1,005,802
Other consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans	405,709	419,968
Total consumer
Loans and Leases Receivable Disclosure [Line Items]
Total loans	$ 7,410,200	$ 7,209,037