Business Combinations - Narrative (Details)			5 Months Ended	6 Months Ended
	Jan. 03, 2022 USD ($) branch $ / shares shares	Aug. 06, 2021 USD ($) branch $ / shares shares	Dec. 31, 2021 USD ($)	Jun. 30, 2022 USD ($) branch	Mar. 31, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
Allowance for credit losses			$ 83,315,000	$ 90,769,000	$ 89,838,000	$ 81,127,000	$ 86,643,000	$ 92,733,000
Apollo Bancshares, Inc.
Business Acquisition [Line Items]
Number of branches operated | branch				5
Deposits to be acquired in acquisition				$ 930,300,000
Loans to be acquired in acquisition				$ 736,000,000
Drummond Banking Company
Business Acquisition [Line Items]
Number of branches operated | branch				18
Deposits to be acquired in acquisition				$ 919,000,000
Loans to be acquired in acquisition				$ 570,900,000
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 recognized from acquisition, nondeductible	$ 8,000,000
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)	0.7997	0.1703
Goodwill recognized from acquisition, nondeductible		$ 31,000,000
Fair value of options converted	$ 497,000	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