Loans and Other Real Estate - Lakeland 's Commercial Loan Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 5,097,820	$ 4,419,045
Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,589,593	3,057,779
Commercial, secured by real estate | 1
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial, secured by real estate | 2
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial, secured by real estate | 3
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,072	69,995
Commercial, secured by real estate | 4
Financing Receivable, Recorded Investment [Line Items]
Total loans	965,825	933,577
Commercial, secured by real estate | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,332,863	1,910,423
Commercial, secured by real estate | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	100,347	61,626
Commercial, secured by real estate | 6 - Other assets especially mentioned
Financing Receivable, Recorded Investment [Line Items]
Total loans	55,438	38,844
Commercial, secured by real estate | 7 - Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	61,048	43,314
Commercial, secured by real estate | 8 - Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial, secured by real estate | 9 - Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial, industrial and other
Financing Receivable, Recorded Investment [Line Items]
Total loans	431,934	336,735
Commercial, industrial and other | 1
Financing Receivable, Recorded Investment [Line Items]
Total loans	898	1,119
Commercial, industrial and other | 2
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,988	18,462
Commercial, industrial and other | 3
Financing Receivable, Recorded Investment [Line Items]
Total loans	39,112	36,367
Commercial, industrial and other | 4
Financing Receivable, Recorded Investment [Line Items]
Total loans	107,376	91,145
Commercial, industrial and other | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	215,975	168,474
Commercial, industrial and other | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	30,192	7,798
Commercial, industrial and other | 6 - Other assets especially mentioned
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,328	2,033
Commercial, industrial and other | 7 - Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,065	11,337
Commercial, industrial and other | 8 - Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Commercial, industrial and other | 9 - Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Real estate - construction
Financing Receivable, Recorded Investment [Line Items]
Total loans	335,169	319,545
Real estate - construction | 1
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Real estate - construction | 2
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Real estate - construction | 3
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Real estate - construction | 4
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,941	17,375
Real estate - construction | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	307,824	297,625
Real estate - construction | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,959	3,493
Real estate - construction | 6 - Other assets especially mentioned
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Real estate - construction | 7 - Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,445	1,052
Real estate - construction | 8 - Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Real estate - construction | 9 - Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Total Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,356,696	3,714,059
Total Commercial Loans | 1
Financing Receivable, Recorded Investment [Line Items]
Total loans	898	1,119
Total Commercial Loans | 2
Financing Receivable, Recorded Investment [Line Items]
Total loans	17,988	18,462
Total Commercial Loans | 3
Financing Receivable, Recorded Investment [Line Items]
Total loans	113,184	106,362
Total Commercial Loans | 4
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,091,142	1,042,097
Total Commercial Loans | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,856,662	2,376,522
Total Commercial Loans | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	137,498	72,917
Total Commercial Loans | 6 - Other assets especially mentioned
Financing Receivable, Recorded Investment [Line Items]
Total loans	66,766	40,877
Total Commercial Loans | 7 - Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	72,558	55,703
Total Commercial Loans | 8 - Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Total Commercial Loans | 9 - Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 0	$ 0