Non-performing Loans and Impaired Loans - Collateral Pledged Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	$ 3,978,382	$ 3,634,596
Real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	1,004,796	920,998
Real estate | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	682,695	751,019
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	2,312,715	2,047,646
Commercial | Owner occupied real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	501,198	519,577
Commercial | Non-owner occupied real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	1,009,116	973,331
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	761,378	$ 505,859
Collateral Pledged [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	4,394
Collateral Pledged [Member] | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	4,394
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	506
Collateral Pledged [Member] | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Total collateral dependent loans	$ 870