Loans and Leases Portfolio (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Loan and lease portfolio
Loans and Leases	$ 7,178,628,000	$ 6,209,857,000	$ 6,897,589,000
Net gains related to sales of mortgage loans	500,000	700,000
Commercial
Loan and lease portfolio
Loans and Leases	2,955,110,000	2,572,163,000	2,828,128,000
Commercial and Industrial
Loan and lease portfolio
Loans and Leases	1,141,408,000		1,055,243,000
Commercial Mortgage
Loan and lease portfolio
Loans and Leases	1,477,902,000		1,437,513,000
Construction
Loan and lease portfolio
Loans and Leases	111,381,000		109,183,000
Lease Financing
Loan and lease portfolio
Loans and Leases	224,419,000		226,189,000
Consumer
Loan and lease portfolio
Loans and Leases	4,223,518,000	3,637,694,000	4,069,461,000
Residential Mortgage
Loan and lease portfolio
Loans and Leases	2,699,434,000		2,571,090,000
Home Equity
Loan and lease portfolio
Loans and Leases	884,742,000		866,688,000
Automobile
Loan and lease portfolio
Loans and Leases	339,686,000		323,848,000
Other
Loan and lease portfolio
Loans and Leases	$ 299,656,000		$ 307,835,000