Business Combinations - Narrative (Details)				3 Months Ended		9 Months Ended
	Jan. 31, 2023 USD ($) branch	Oct. 07, 2022 USD ($) branch	Jan. 03, 2022 USD ($) branch	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Business Acquisition [Line Items]
Goodwill				$ 731,970,000		$ 731,970,000			$ 480,319,000
Allowance for credit losses				149,661,000	$ 95,329,000	149,661,000	$ 95,329,000	$ 159,715,000	$ 113,895,000	$ 90,769,000	$ 83,315,000
Acquisition costs				$ 0	$ 2,100,000	$ 33,200,000	$ 11,800,000
Professional Holding Corp.
Business Acquisition [Line Items]
Number of branches operated | branch	9
Percentage of common stock acquired	100.00%
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)	0.8909
Goodwill	$ 251,226,000
Measurement period adjustment, acquired loan	5,544,000
Measurement period adjustment, receivable	2,409,000
Fair value of options and warrants converted	10,304,000
Allowance for credit losses	45,500,000
Professional Holding Corp. | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses at acquisition	18,879,000
Professional Holding Corp. | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses	$ 26,600,000
Apollo Bancshares, Inc.
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
Goodwill		$ 90,488,000
Measurement period adjustment, acquired loan		0
Measurement period adjustment, receivable		(251,000)
Fair value of options and warrants converted		6,530,000
Allowance for credit losses		$ 7,800,000
Minority interest portion, number of Seacoast stock for each share of stock converted (in shares)		1.195651
Apollo Bancshares, Inc. | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses at acquisition		$ 2,658,000
Apollo Bancshares, Inc. | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses		$ 5,100,000
Drummond Banking Company
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
Goodwill		$ 103,649,000
Goodwill recognized from acquisition, nondeductible		103,600,000
Measurement period adjustment, acquired loan		0
Measurement period adjustment, receivable		(173,000)
Allowance for credit losses		12,500,000
Drummond Banking Company | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses at acquisition		2,566,000
Drummond Banking Company | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses		$ 9,900,000
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			$ 7,962,000
Goodwill recognized from acquisition, nondeductible			8,000,000
Fair value of options and warrants converted			497,000
Allowance for credit losses			1,800,000
Business Bank of Florida | Stock Option | Seacoast 2021 Incentive Plan
Business Acquisition [Line Items]
Fair value of options and warrants converted			500,000
Business Bank of Florida | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses			15,000
Allowance for credit losses at acquisition			15,000
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			$ 26,489,000
Goodwill recognized from acquisition, nondeductible			26,500,000
Fair value of options and warrants converted			3,336,000
Allowance for credit losses			3,400,000
Sabal Palm Bancorp, Inc. | Stock Option | Seacoast 2021 Incentive Plan
Business Acquisition [Line Items]
Fair value of options and warrants converted			3,300,000
Sabal Palm Bancorp, Inc. | PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses			37,000
Allowance for credit losses at acquisition			37,000
Sabal Palm Bancorp, Inc. | Acquired Non-PCD Loans
Business Acquisition [Line Items]
Allowance for credit losses			$ 3,400,000