Business Combinations - Additional Information (Details) $ / shares in Units, shares in Thousands			1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 11, 2016 USD ($)	Jul. 15, 2015 USD ($)	Jul. 17, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Nov. 03, 2016 USD ($)	Jun. 03, 2016 USD ($)
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Deposit Premium Percentage									3.00%
Business Combination, Bargain Purchase, Gain Recognized, Amount			$ (416,000)		$ 0	$ 416,000	$ 0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount	$ 32,000,000
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Loan Held For Sale									$ 314,000,000
Business Loan Premium									0.50%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable									$ 63,000,000
Business Acquisition Intangible Assets Expected Tax Deductible Amount									$ 13,000,000
Business Acquisition Intangible Assets Tax Deductible Period					15 years
Bank shares, Inc [Member]
Business Acquisition [Line Items]
Business Acquisition Per Share Exchange Ratio		0.3114
Payments to Acquire Businesses, Gross		$ 1,481,000,000
Payments for Merger Related Costs					$ 3,100,000
Business Combination, Bargain Purchase, Gain Recognized, Amount				$ 416,000
Bank shares, Inc [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired					100.00%
Stock Issued During Period, Shares, Acquisitions | shares			1,090
Shares Issued, Price Per Share | $ / shares			$ 15.75
Floridian Financial Group [Member]
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Liabilities Deposits	337,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	417,000,000
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 equals 35% cash and 65% Seacoast shares (based on Seacoasts closing price of $15.47 per share on March 11, 2016).
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Assets Loans	$ 267,000,000
Gulf Shore Banc Shares Inc [Member]
Business Acquisition [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Liabilities Deposits								$ 276,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets								328,000,000
Business Acquisition, Equity Interest Issued or Issuable, Description					Under the terms of the definitive agreement, each share of GulfShore common stock (except for specified shares of GulfShore common stock held by GulfShore or Seacoast and any dissenting shares) will be converted into the right to receive the combination of $1.47 in cash and 0.4807 shares of Seacoast common stock.
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Noncurrent Assets Loans								$ 262,000,000
Series B Preferred Stock [Member] | Bank shares, Inc [Member]
Business Acquisition [Line Items]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 1,000
Payments to Acquire Businesses, Gross			$ 1,480,000
Stock Issued During Period, Value, Acquisitions			$ 18,700,000
Series A Preferred Stock [Member] | Bank shares, Inc [Member]
Business Acquisition [Line Items]
Business Acquisition Per Share Exchange Ratio			0.3114