Loans and Leases and Other Real Estate - Lakeland 's Commercial Loan Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 4,419,045	$ 4,117,265
Commercial, secured by real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,057,779	2,831,184
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	69,995	76,824
Commercial, secured by real estate | 4
Financing Receivable, Recorded Investment [Line Items]
Total loans	933,577	862,537
Commercial, secured by real estate | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,910,423	1,779,908
Commercial, secured by real estate | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	61,626	47,178
Commercial, secured by real estate | 6 - Other assets especially mentioned
Financing Receivable, Recorded Investment [Line Items]
Total loans	38,844	40,245
Commercial, secured by real estate | 7 - Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	43,314	24,492
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	336,735	340,400
Commercial, industrial and other | 1
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,119	392
Commercial, industrial and other | 2
Financing Receivable, Recorded Investment [Line Items]
Total loans	18,462	26,968
Commercial, industrial and other | 3
Financing Receivable, Recorded Investment [Line Items]
Total loans	36,367	35,950
Commercial, industrial and other | 4
Financing Receivable, Recorded Investment [Line Items]
Total loans	91,145	96,426
Commercial, industrial and other | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	168,474	150,928
Commercial, industrial and other | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,798	8,779
Commercial, industrial and other | 6 - Other assets especially mentioned
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,033	8,670
Commercial, industrial and other | 7 - Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,337	12,287
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	319,545	264,908
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	17,375	15,502
Real estate - construction | 5
Financing Receivable, Recorded Investment [Line Items]
Total loans	297,625	246,806
Real estate - construction | 5W - Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,493	0
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	1,052	2,600
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