Accounting Policies - Impact of ASC 326 (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans	$ 56,319	$ 55,090	$ 22,577	$ 17,667	$ 17,956	$ 18,305	$ 17,820
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			13,618
Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			4,048
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans	$ 1,250	$ 1,190	0	1,077	$ 1,041	$ 1,040	$ 1,006
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			4,911
As Reported Under ASC 326
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			40,244
As Reported Under ASC 326 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			25,614
As Reported Under ASC 326 | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			4,971
As Reported Under ASC 326 | Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			1,077
As Reported Under ASC 326 | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			8,582
Impact of adopting ASC 326
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			17,667	19,791
Impact of adopting ASC 326 | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			11,996
Impact of adopting ASC 326 | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			923
Impact of adopting ASC 326 | Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			1,077	$ 0
Impact of adopting ASC 326 | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans			$ 3,671