BUSINESS COMBINATIONS - Additional Information (Details) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended	3 Months Ended	9 Months Ended
	Nov. 03, 2015 USD ($)	Jul. 17, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Oct. 14, 2015 USD ($)
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross				$ 1,481
The Bank shares Inc [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired			100.00%	100.00%
Business Acquisition Per Share Exchange Ratio		0.3114
Payments to Acquire Businesses, Gross		$ 1,481,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		$ 14,163
Payments for Merger Related Costs			$ 2,700
The Bank shares Inc [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions | shares		1,090
Shares Issued, Price Per Share | $ / shares		$ 15.75
BMO Harris Central [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Liabilities Deposits					$ 355,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Liabilities Deposits Checking Accounts Percentage					56.00%
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Deposit Premium Percentage					3.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets					$ 70,000
Floridian Financial Group [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Liabilities Deposits	$ 361,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	$ 426,000
Business Acquisition, Equity Interest Issued or Issuable, Description	Under the terms of the definitive agreement, Floridian shareholders will have the right to receive, at their election, (i) the combination of $4.29 in cash and 0.5291 shares of Seacoast common stock, (ii) $12.25 in cash, or (iii) 0.8140 shares of Seacoast common stock, subject to a customary proration mechanism so that the aggregate consideration mix equals 35% cash and 65% Seacoast shares (based on Seacoasts ten-day average closing price of $15.05 per share as of October 29, 2015).
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Assets Loans	$ 289,000
Series B Preferred Stock [Member] | The Bank shares Inc [Member]
Business Acquisition [Line Items]
Preferred Stock, Par or Stated Value Per Share | $ / shares		$ 1,000
Payments to Acquire Businesses, Gross		$ 1,480
Stock Issued During Period, Value, Acquisitions		$ 18,700
Series A Preferred Stock [Member]
Business Acquisition [Line Items]
Business Acquisition Per Share Exchange Ratio				0.3114