Shareholders' Equity - Summary of Required Regulatory Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Parent Company
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Risk-Based Capital Ratio (to risk-weighted assets), Amount	$ 860,934	$ 744,687
Tier 1 Capital (to risk-weighted assets), Amount	825,640	712,144
Common Equity Tier 1 Capital (to risk-weighted assets), Amount	754,555	641,340
Leverage (to adjusted average assets), Amount	$ 825,640	$ 712,144
Total Risk-Based Capital Ratio (to risk-weighted assets), Ratio	15.71%	14.43%
Tier 1 Capital (to risk-weighted assets), Ratio	15.06%	13.80%
Common Equity Tier 1 Capital (to risk-weighted assets), Ratio	13.77%	12.43%
Leverage (to adjusted average assets), Ratio	12.20%	11.16%
Total Risk-Based Capital Ratio (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Amount	$ 438,506	$ 412,754
Tier 1 Capital (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Amount	328,880	309,566
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum for Capital, Adequacy Purpose, Amount	246,660	232,174
Leverage (to adjusted average assets), Minimum for Capital Adequacy Purpose, Amount	$ 270,788	$ 255,167
Total Risk-Based Capital Ratio (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Ratio	8.00%	8.00%
Tier 1 Capital (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Ratio	6.00%	6.00%
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum for Capital, Adequacy Purpose, Ratio	4.50%	4.50%
Leverage (to adjusted average assets), Minimum for Capital Adequacy Purpose, Ratio	4.00%	4.00%
Seacoast National Bank (A Wholly Owned Bank Subsidiary)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Risk-Based Capital Ratio (to risk-weighted assets), Amount	$ 804,058	$ 701,093
Tier 1 Capital (to risk-weighted assets), Amount	768,764	668,550
Common Equity Tier 1 Capital (to risk-weighted assets), Amount	768,764	668,550
Leverage (to adjusted average assets), Amount	$ 768,764	$ 668,550
Total Risk-Based Capital Ratio (to risk-weighted assets), Ratio	14.68%	13.60%
Tier 1 Capital (to risk-weighted assets), Ratio	14.04%	12.97%
Common Equity Tier 1 Capital (to risk-weighted assets), Ratio	14.04%	12.97%
Leverage (to adjusted average assets), Ratio	11.38%	10.49%
Total Risk-Based Capital Ratio (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Amount	$ 437,952	$ 412,486
Tier 1 Capital (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Amount	328,464	309,364
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum for Capital, Adequacy Purpose, Amount	246,348	232,023
Leverage (to adjusted average assets), Minimum for Capital Adequacy Purpose, Amount	$ 270,230	$ 255,036
Total Risk-Based Capital Ratio (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Ratio	8.00%	8.00%
Tier 1 Capital (to risk-weighted assets), Minimum for Capital Adequacy Purpose, Ratio	6.00%	6.00%
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum for Capital, Adequacy Purpose, Ratio	4.50%	4.50%
Leverage (to adjusted average assets), Minimum for Capital Adequacy Purpose, Ratio	4.00%	4.00%
Total Risk-Based Capital Ratio (to risk-weighted assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 547,440	$ 515,607
Tier 1 Capital (to risk-weighted assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	437,952	412,486
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	355,836	335,145
Leverage (to adjusted average assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 337,787	$ 318,795
Total Risk-Based Capital Ratio (to risk-weighted assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Capital (to risk-weighted assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.50%	6.50%
Leverage (to adjusted average assets), Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%

Common equity capital as defined in the regulations. Also called Core Capital.

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The minimum Tier common equity Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Risk Based Common Equity Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 common equity capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Common equity tier 1 capital divided by risk weighted assets as defined by regulations.

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The amount of total capital as defined in the regulations.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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Tier 1 Risk Based Capital as defined in the regulations.

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