Non-performing Loans and Impaired Loans - Collateral Pledged Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	$ 3,707,299	$ 3,634,596
Real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	981,048	920,998
Real estate | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	733,034	751,019
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	2,050,402	2,047,646
Commercial | Owner occupied real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	510,901	519,577
Commercial | Non-owner occupied real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	992,595	973,331
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	502,247	$ 505,859
Collateral Pledged [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	4,439
Collateral Pledged [Member] | Real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	681
Collateral Pledged [Member] | Real estate | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	681
Collateral Pledged [Member] | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	3,758
Collateral Pledged [Member] | Commercial | Owner occupied real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	3,018
Collateral Pledged [Member] | Commercial | Non-owner occupied real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	114
Collateral Pledged [Member] | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	$ 626