Loans and Allowance for Loan Losses (Narrative) (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) contract	Mar. 31, 2019 USD ($) contract	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recognized, cash basis	$ 961,000	$ 648,000
Loans pledged as collateral	$ 15,240,000,000		$ 12,110,000,000
ACL to loans ratio	1.39%
CECL estimates qualitative overlay	$ 37,300,000
Basis points added to allowance for credit losses	0.10%
Recorded Investment	$ 36,695,000	$ 7,507,000
Commitments to land additional funds to TDRs	$ 0		$ 0
Troubled Debt Restructuring That Subsequently Defaults
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of contracts | contract	3	0
Recorded Investment	$ 618,000
Interest Income Recorded
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recognized	$ 2,100,000	$ 2,100,000
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan substandard period (in days)	90 days
Loss And Charged Off
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan charge off (in days)		120 days