PARENT COMPANY STATEMENTS - CONDENSED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Other income									$ 3,564	$ 2,857	$ 2,098
Interest expense on subordinated debt	$ (5,141)	$ (6,066)	$ (7,303)	$ (11,585)	$ (13,430)	$ (15,224)	$ (16,224)	$ (15,285)	(30,095)	(60,163)	(47,699)
INCOME BEFORE INCOME TAXES AND EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									103,876	107,385	98,944
Income tax benefit	(6,071)	(5,377)	(4,448)	(3,643)	(5,431)	(5,119)	(5,409)	(4,379)	(19,539)	(20,338)	(18,533)
NET INCOME	$ 24,592	$ 22,776	$ 19,670	$ 17,299	$ 22,198	$ 21,454	$ 21,713	$ 21,682	84,337	87,047	80,411
COMPREHENSIVE INCOME									100,022	105,297	75,131
Reportable Legal Entities | Parent Company
Condensed Financial Statements, Captions [Line Items]
Other income										155	171
Interest expense on subordinated debt										(1,720)	(1,643)
Miscellaneous expense									(3,935)	(5,321)	(6,422)
INCOME BEFORE INCOME TAXES AND EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									29,444	52,258	21,049
Income tax benefit									1,065	2,256	2,795
INCOME BEFORE EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									30,509	54,514	23,844
Equity in undistributed income of subsidiaries									53,828	32,533	56,567
NET INCOME									84,337	87,047	80,411
COMPREHENSIVE INCOME									100,022	105,297	75,131
Reportable Legal Entities | Parent Company | Lake City Bank
Condensed Financial Statements, Captions [Line Items]
Dividends from Lake City Bank, Lakeland Statutory Trust II									32,079	57,842	27,933
Reportable Legal Entities | Parent Company | Non-bank Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Dividends from Lake City Bank, Lakeland Statutory Trust II									$ 1,300	$ 1,302	$ 1,010