Business Combinations - Purchase Price (Details) $ / shares in Units, $ in Thousands	Oct. 19, 2018 USD ($) $ / shares shares	Nov. 03, 2017 USD ($) $ / shares shares	Oct. 20, 2017 USD ($) $ / shares shares	Apr. 07, 2017 USD ($) $ / shares shares
Gulf Shore Banc shares Inc
Business Acquisition [Line Items]
Value of shares exchanged for cash				$ 8,034
Number of shares outstanding (in shares) | shares				5,464,000
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)				0.4807
Number of shares of Seacoast common stock issued (in shares) | shares				2,627,000
Multiplied by common stock price per share (in dollars per share) | $ / shares				$ 23.94
Value of common stock issued				$ 62,883
Total purchase price				$ 70,917
NorthStar Bank
Business Acquisition [Line Items]
Value of shares exchanged for cash			$ 4,701
Number of shares outstanding (in shares) | shares			1,958,000
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)			0.5605
Number of shares of Seacoast common stock issued (in shares) | shares			1,098,000
Multiplied by common stock price per share (in dollars per share) | $ / shares			$ 24.92
Value of common stock issued			$ 27,353
Cash paid for NorthStar Banking vested Corporation stock options			801
Total purchase price			$ 32,855
Palm Beach Community Bank
Business Acquisition [Line Items]
Value of shares exchanged for cash		$ 15,694
Number of shares outstanding (in shares) | shares		2,507,000
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)		0.924
Number of shares of Seacoast common stock issued (in shares) | shares		2,316,000
Multiplied by common stock price per share (in dollars per share) | $ / shares		$ 24.31
Value of common stock issued		$ 56,312
Total purchase price		$ 72,006
First Green Bancorp, Inc. | Subsequent Event
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 Seacoast 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 NorthStar Banking vested Corporation stock options	6,558
Total purchase price	$ 114,044