PARENT COMPANY STATEMENTS - CONDENSED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Other income									$ 4,548	$ 2,573	$ 2,629
Interest expense on subordinated debt	$ (13,430)	$ (15,224)	$ (16,224)	$ (15,285)	$ (14,138)	$ (12,454)	$ (11,262)	$ (9,845)	(60,163)	(47,699)	(29,806)
INCOME BEFORE INCOME TAX EXPENSE									107,385	98,944	89,634
Income tax benefit	(5,431)	(5,119)	(5,409)	(4,379)	(5,480)	(4,679)	(5,110)	(3,264)	(20,338)	(18,533)	(32,304)
NET INCOME	$ 22,198	$ 21,454	$ 21,713	$ 21,682	$ 21,363	$ 20,570	$ 20,142	$ 18,336	87,047	80,411	57,330
COMPREHENSIVE INCOME									105,297	75,131	59,047
Reportable Legal Entities [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Other income									155	171	57
Interest expense on subordinated debt									(1,720)	(1,643)	(1,349)
Miscellaneous expense									(5,321)	(6,422)	(6,491)
INCOME BEFORE INCOME TAX EXPENSE									52,258	21,049	15,069
Income tax benefit									2,256	2,795	2,688
INCOME BEFORE EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									54,514	23,844	17,757
Equity in undistributed income of subsidiaries									32,533	56,567	39,573
NET INCOME									87,047	80,411	57,330
COMPREHENSIVE INCOME									105,297	75,131	59,047
Reportable Legal Entities [Member] | Parent Company [Member] | Lake City Bank [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from Lake City Bank, Lakeland Statutory Trust II									57,842	27,933	21,822
Reportable Legal Entities [Member] | Parent Company [Member] | Non-bank Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from Lake City Bank, Lakeland Statutory Trust II									$ 1,302	$ 1,010	$ 1,030