Business Combinations - Additional Information (Details) $ / shares in Units, $ in Thousands							1 Months Ended
	Jun. 11, 2018 branch	Nov. 03, 2017 USD ($) $ / shares	Nov. 03, 2017 USD ($) branch $ / shares	Oct. 20, 2017 USD ($) branch $ / shares	Apr. 07, 2017 USD ($) $ / shares	Apr. 07, 2017 USD ($) branch $ / shares	Feb. 28, 2018 branch	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Deposits								$ 4,697,440		$ 4,592,720
Loans, net								$ 3,945,092		$ 3,790,255
Gulf Shore Banc shares Inc
Business Acquisition [Line Items]
Number of branches acquired | branch						3
Other assets acquired					$ 358,000	$ 358,000
Loans acquired					251,000	251,000
Deposits acquired					$ 285,000	$ 285,000
Percentage of common stock acquired					100.00%	100.00%
Cash portion, cash per share for common stock converted (in dollars per share) | $ / shares						$ 1.47
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)						0.4807
Multiplied by common stock price per share (in dollars per share) | $ / shares					$ 23.94	$ 23.94
Goodwill recognized from acquisition, nondeductible					$ 37,100
NorthStar Bank
Business Acquisition [Line Items]
Number of branches acquired | branch				3
Other assets acquired				$ 216,000
Loans acquired				137,000
Deposits acquired				$ 182,000
Percentage of common stock acquired				100.00%
Cash portion, cash per share for common stock converted (in dollars per share) | $ / shares				$ 2.40
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)				0.5605
Multiplied by common stock price per share (in dollars per share) | $ / shares				$ 24.92
Goodwill recognized from acquisition, nondeductible				$ 12,300
Palm Beach Community Bank
Business Acquisition [Line Items]
Number of branches acquired | branch							2
Other assets acquired		$ 357,000	$ 357,000
Loans acquired		270,000	270,000
Deposits acquired		$ 269,000	$ 269,000
Percentage of common stock acquired		100.00%	100.00%
Cash portion, cash per share for common stock converted (in dollars per share) | $ / shares			$ 6.26
Common stock portion, number of Seacoast stock for each share of stock converted (in shares)			0.924
Multiplied by common stock price per share (in dollars per share) | $ / shares		$ 24.31	$ 24.31
Goodwill recognized from acquisition, nondeductible		$ 34,800
Palm Beach Community Bank
Business Acquisition [Line Items]
Number of branches operated | branch			4
First Green Bancorp, Inc.
Business Acquisition [Line Items]
Number of branches operated | branch	7
Deposits									$ 629,000
Loans, net									$ 629,000