Assets and Liabilities Measured at Fair Value - Fair values for other financial instruments that are not measured at fair value on recurring basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Securities held-to-maturity	$ 301,595	$ 287,904
Carrying Amount
Assets:
Securities held-to-maturity	290,404	283,533
Loans and leases, net	8,853,519	8,750,464
Liabilities:
Deposits	11,034,926	10,897,244
Long-term debt	212,849	212,664
Fair Value
Assets:
Securities held-to-maturity	301,595	287,904
Loans and leases, net	8,690,538	8,714,592
Liabilities:
Deposits	11,037,183	10,897,465
Long-term debt	213,940	217,665
Fair Value | Level 1
Assets:
Securities held-to-maturity	0	0
Loans and leases, net	0	0
Liabilities:
Deposits	0	0
Long-term debt	0	0
Fair Value | Level 2
Assets:
Securities held-to-maturity	301,595	287,904
Loans and leases, net	0	0
Liabilities:
Deposits	11,037,183	10,897,465
Long-term debt	0	0
Fair Value | Level 3
Assets:
Securities held-to-maturity	0	0
Loans and leases, net	8,690,538	8,714,592
Liabilities:
Deposits	0	0
Long-term debt	$ 213,940	$ 217,665