Accounting Policies - Impact of ASC 326 (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses on loans	$ 48,440	$ 22,577	$ 17,667	$ 17,821	$ 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	$ 1,055	0	1,077	$ 1,014	$ 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