Loans and Leases - Commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans and leases
Loan and lease commitments	$ 5,419,907	$ 5,401,763
Real estate
Loans and leases
Loan and lease commitments	1,553,165	1,509,914
Commercial and Industrial
Loans and leases
Loan and lease commitments	2,365,231	2,406,261
Commercial Real Estate | Real estate
Loans and leases
Loan and lease commitments	78,275	78,266
Construction | Real estate
Loans and leases
Loan and lease commitments	481,366	450,856
Residential | Real estate
Loans and leases
Loan and lease commitments	993,524	980,792
Consumer
Loans and leases
Loan and lease commitments	$ 1,501,511	$ 1,485,588