Loans and Leases and Other Real Estate - Lakeland's Non-Accrual Loans and Leases and Its Accruing Troubled Debt Restructurings (TDRs) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	$ 13,655	$ 20,404
Other real estate and other repossessed assets	843	1,072
TOTAL NON-PERFORMING ASSETS	14,498	21,476
Troubled debt restructurings, still accruing	11,462	8,802
Commercial, secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	5,890	10,413
Commercial, industrial and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	184	167
Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	144	153
Real estate - residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	3,860	6,048
Real estate - construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	1,472	1,472
Home equity and consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans and leases	$ 2,105	$ 2,151