BUSINESS COMBINATIONS - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended
	Mar. 11, 2016	Mar. 31, 2017	May 04, 2017	Apr. 07, 2017	Jun. 03, 2016
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deposit Premium Percentage					3.00%
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Loan Held For Sale					$ 314
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable					63
Business Acquisition Intangible Assets Expected Tax Deductible Amount					$ 13
Business Acquisition Intangible Assets Tax Deductible Period		15 years
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount	$ 32
Business Loan Premium					0.50%
Floridian Financial Group [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	417
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Deposits	337
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Assets Loans	$ 267
Business Acquisition, Equity Interest Issued or Issuable, Description		Under the terms of the definitive agreement, Floridian shareholders received, 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 equaled 35% cash and 65% Seacoast shares (based on Seacoasts closing price of $15.47 per share on March 11, 2016).
Floridian Financial Group [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Gulf Shore Banc shares Inc [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Description		Under the terms of the definitive agreement, GulfShore shareholders received the combination of $1.47 in cash and 0.4807 shares of Seacoast common stock (based on Seacoasts closing price of $23.94 per share on April 7, 2017).
Gulf Shore Banc shares Inc [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets				$ 321
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Deposits				285
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Assets Loans				$ 258
Gulf Shore Banc shares Inc [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Palm Beach Community Bank [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Deposits			$ 281
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Assets Loans			$ 290