Business Combinations - Purchase Price (Details) $ / shares in Units, $ in Thousands	Aug. 21, 2020 USD ($) $ / shares shares	Mar. 13, 2020 USD ($) $ / shares shares	Oct. 19, 2018 USD ($) $ / shares shares
Fourth Street Banking Company
Business Acquisition [Line Items]
Number of shares outstanding (in shares) | shares	11,220,000
Shares issued upon conversion of convertible debt (in shares) | shares	5,405,000
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)	0.1275
Number of shares of common stock issued (in shares) | shares	2,120,000
Multiplied by common stock price per share (in dollars per share) | $ / shares	$ 19.40
Value of common stock issued	$ 41,121
Cash paid for vested Corporation stock options	596
Total purchase price	$ 41,717
First Bank of The Palm Beaches
Business Acquisition [Line Items]
Number of shares outstanding (in shares) | shares		5,213,000
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)		0.2000
Number of shares of common stock issued (in shares) | shares		1,043,000
Multiplied by common stock price per share (in dollars per share) | $ / shares		$ 20.17
Value of common stock issued		$ 21,031
Cash paid for vested Corporation stock options		866
Total purchase price		$ 21,897
First Green Bancorp, Inc.
Business Acquisition [Line Items]
Number of shares outstanding (in shares) | shares			5,462,000
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)			0.7324
Number of shares of common stock issued (in shares) | shares			4,000,000
Multiplied by common stock price per share (in dollars per share) | $ / shares			$ 26.87
Value of common stock issued			$ 107,486
Cash paid for vested Corporation stock options			6,558
Total purchase price			$ 114,044