Loans and Leases and Other Real Estate - Composition of Lakeland`s Loan and Lease Portfolio (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 4,460,447	$ 4,156,680
Less deferred fees	(3,714)	(3,960)
Loans and leases, net of deferred fees	4,456,733	4,152,720
Commercial, secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	3,057,779	2,831,184
Commercial, industrial and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	336,735	340,400
Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	87,925	75,039
Real estate - residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	329,854	322,880
Real estate - construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	319,545	264,908
Home equity and consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 328,609	$ 322,269