Loans - Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) contract	Mar. 31, 2019 USD ($) contract	Mar. 31, 2020 USD ($) contract	Dec. 31, 2019 USD ($)	Mar. 13, 2020 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Deferred costs	$ 20,900,000		$ 20,900,000	$ 19,900,000
Accrued interest receivable	15,200,000		15,200,000	14,900,000
Interest income from securities with no related allowance	300,000	$ 300,000
Allowance for credit loss on TDRs	$ 100,000	$ 0	$ 100,000
Number of loans under trouble debt restructuring | contract	5	2	3
Value of loans under trouble debt restructuring	$ 482,000	$ 1,995,000	$ 1,400,000
Interest income related to impaired loans with impairment measured on present value of expected future cash flows	24,000	$ 35,000
First Bank of the Palm Beaches
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans acquired in acquisition					$ 146,839,000
Loans | Bank Shares, Inc
Financing Receivable, Troubled Debt Restructuring [Line Items]
Remaining fair value adjustment for loans acquired	$ 32,900,000			$ 34,900,000
Percentage of fair value adjustment for loans acquired	3.40%		3.40%	3.80%
PCD Loans | First Bank of the Palm Beaches
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans acquired in acquisition	$ 43,000,000.0		$ 43,000,000.0		$ 43,038,000
PCD Loans | Loans | Bank Shares, Inc
Financing Receivable, Troubled Debt Restructuring [Line Items]
Remaining fair value adjustment for loans acquired	1,000,000.0
Non-PCD Loans | First Bank of the Palm Beaches
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans acquired in acquisition	103,800,000		103,800,000
Non-PCD Loans | Loans | Bank Shares, Inc
Financing Receivable, Troubled Debt Restructuring [Line Items]
Remaining fair value adjustment for loans acquired	31,900,000
CARES Act, Purchase Protection Plan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Value of loans deferred, not classified as TDRs	$ 512,000,000		$ 512,000,000