Seacoast Banking Corporation of Florida (Parent Company Only) Financial Information - Summary of Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Total Assets	$ 8,342,392	$ 7,108,511
Liabilities and Shareholders' Equity
Subordinated debt	71,365	71,085
Shareholders' equity	1,130,402	985,639	$ 864,267	$ 689,664
Total Liabilities & Shareholders' Equity	8,342,392	7,108,511
Parent Company
Assets
Cash	70	70
Securities purchased under agreement to resell with subsidiary bank, maturing within 30 days	70,074	52,979
Investment in subsidiaries	1,134,536	1,005,756
Other assets	659	1,515
Total Assets	1,205,339	1,060,320
Liabilities and Shareholders' Equity
Subordinated debt	71,365	71,085
Other liabilities	3,676	3,700
Shareholders' equity	1,130,298	985,535
Total Liabilities & Shareholders' Equity	$ 1,205,339	$ 1,060,320