Business Combinations - Narrative (Details)				5 Months Ended	9 Months Ended
	Oct. 07, 2022 USD ($) branch	Jan. 03, 2022 USD ($) branch $ / shares shares	Aug. 06, 2021 USD ($) branch $ / shares shares	Dec. 31, 2021 USD ($)	Sep. 30, 2022 USD ($) branch	Jun. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Allowance for credit losses				$ 83,315,000	$ 95,329,000	$ 90,769,000	$ 87,823,000	$ 81,127,000	$ 92,733,000
Professional Holding Corp.
Business Acquisition [Line Items]
Number of branches operated | branch					9
Deposits to be acquired in acquisition					$ 2,200,000,000
Loans to be acquired in acquisition					$ 2,000,000,000
Business Bank of Florida
Business Acquisition [Line Items]
Number of branches operated | branch		1
Percentage of common stock acquired		100.00%
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)		0.7997
Goodwill recognized from acquisition, nondeductible		$ 8,000,000
Fair value of options converted		497,000
Allowance for credit losses		1,800,000
Deposits to be acquired in acquisition		$ 166,326,000
Business Bank of Florida | Stock Option | Seacoast 2021 Incentive Plan
Business Acquisition [Line Items]
Shares granted (in shares) | shares		52,432
Weighted-average exercise price, granted (in dollars per share) | $ / shares		$ 26.63
Fair value of options converted		$ 500,000
Business Bank of Florida | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses		15,000
Loans to be acquired in acquisition		651,000
Business Bank of Florida | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses		$ 1,800,000
Sabal Palm Bancorp, Inc.
Business Acquisition [Line Items]
Number of branches operated | branch		3
Percentage of common stock acquired		100.00%
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)		0.2203
Goodwill recognized from acquisition, nondeductible		$ 26,500,000
Fair value of options converted		3,336,000
Allowance for credit losses		3,400,000
Deposits to be acquired in acquisition		$ 395,952,000
Sabal Palm Bancorp, Inc. | Stock Option | Seacoast 2021 Incentive Plan
Business Acquisition [Line Items]
Shares granted (in shares) | shares		188,253
Weighted-average exercise price, granted (in dollars per share) | $ / shares		$ 17.84
Fair value of options converted		$ 3,300,000
Sabal Palm Bancorp, Inc. | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses		37,000
Loans to be acquired in acquisition		3,003,000
Sabal Palm Bancorp, Inc. | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses		$ 3,400,000
Legacy Bank of Florida
Business Acquisition [Line Items]
Number of branches operated | branch			5
Percentage of common stock acquired			100.00%
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)			0.1703
Goodwill recognized from acquisition, nondeductible			$ 31,000,000
Fair value of options converted			4,736,000
Allowance for credit losses			11,200,000
Deposits to be acquired in acquisition			$ 494,921,000
Legacy Bank of Florida | Stock Option | Seacoast 2021 Incentive Plan
Business Acquisition [Line Items]
Shares granted (in shares) | shares			356,497
Weighted-average exercise price, granted (in dollars per share) | $ / shares			$ 16.70
Fair value of options converted			$ 4,700,000
Share-based compensation expense				$ 900,000
Legacy Bank of Florida | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses			3,000,000
Loans to be acquired in acquisition			62,589,000
Legacy Bank of Florida | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses			$ 8,200,000
Apollo Bancshares, Inc. | Subsequent Event
Business Acquisition [Line Items]
Number of branches operated | branch	5
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)	1.006529
Fair value of options converted	$ 6,530,000
Minority interest portion, number of Seacoast stock for each share of stock converted (in shares)	1.195651
Drummond Banking Company | Subsequent Event
Business Acquisition [Line Items]
Number of branches operated | branch	18
Percentage of common stock acquired	100.00%
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)	51.9561