Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation This quarterly report presents the consolidated financial statements of Lakeland Bancorp, Inc. and its subsidiaries, including Lakeland Bank (“Lakeland”) and the Bank’s wholly owned subsidiaries (collectively, the “Company”). The accounting and reporting policies of the Company conform with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and predominant practices within the banking industry. The Company’s unaudited interim financial statements reflect all adjustments, such as normal recurring accruals that are, in the opinion of management, necessary for the fair presentation of the results of the interim periods. The results of operations for the three months ended March 31, 2018 do not necessarily indicate the results that the Company will achieve for all of 2018. Certain information and footnote disclosures required under U.S. GAAP have been condensed or omitted, as permitted by rules and regulations of the Securities and Exchange Commission. These unaudited interim financial statements should be read in conjunction with the audited consolidated financial statements and accompanying notes that are presented in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Certain reclassifications have been made in the consolidated financial statements to conform with current year classifications.
Recent Accounting Pronouncements	In March 2018, the Financial Accounting Standards Board ("FASB") issued an update regarding the accounting implications of the recently issued Tax Cuts and Jobs Act (the "Tax Act"). The update clarifies that in a company's financial statements that include the reporting period in which the Tax Act was enacted, a company must first reflect the income tax effects of the Tax Act in which the accounting under U.S. GAAP is complete. Those amounts would not be provisional amounts. The company would also report provisional amounts for those specific income tax effects for which the accounting under U.S. GAAP will be incomplete but for which a reasonable estimate can be determined. If there are income tax effects for the Tax Act for which a reasonable estimate cannot be determined, the company would not report provisional amounts and would continue to apply U.S. GAAP based on the tax laws that were in effect immediately prior to the Tax Act being enacted. This accounting update is effective immediately. The Company believes its accounting for the the income tax effects of the Tax Act is complete. Technical corrections or other forthcoming guidance could change how we interpret provisions of the Tax Act, which may impact our effective tax rate and could affect our deferred tax assets, tax positions and/or our tax liabilities. In February 2018, the FASB issued an update (ASU 2018-02) regarding the reclassification of certain tax effects from accumulated other comprehensive income. This update requires a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the newly enacted federal corporate tax rate. The amount of the reclassification would be the difference between the historical 35% corporate income tax rate and the newly enacted 21% corporate tax rate. This update eliminates the stranded tax effects associated with the change in the federal corporate income tax rate in the Tax Act and improves the usefulness of information reported to financial statement users. The amendments are effective for all entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption of the amendments is permitted including adoption in any interim period, for public business entities for reporting periods for which financial statements have not yet been issued and all other entities for reporting periods for which financial statements have not yet been made available for issuance. An entity may apply the amendments in the update retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized. The Company elected to adopt this update in December 2017, and recorded a $420,000 increase to retained earnings and reduction to accumulated other comprehensive income in December 2017. In August 2017, the FASB issued an update intended to improve and simplify accounting rules around hedge accounting. Amendments expand and refine hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in this update also make certain targeted improvements to simplify the application of hedge accounting guidance and ease the administrative burden of hedge documentation requirements and assessing hedge effectiveness. This update will be effective for financial statements issued for fiscal years and interim periods beginning after December 15, 2019. The Company is still evaluating the impact that this guidance will have on its financial statements. In July 2017, the FASB issued guidance which simplifies the accounting for certain financial instruments with down round features, a provision in an equity-linked financial instrument (or embedded feature) that provides a downward adjustment of the current exercise price based on the price of future equity offerings. The provisions of the new guidance related to down rounds are effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The adoption of this update is not expected to have a material impact on the Company’s financial statements because the Company does not have any equity-linked financial instruments that have such down round features. In May 2017, the FASB issued an update which provides clarity and reduces diversity in practice when accounting for the modification of terms and conditions for share-based payment awards. Previous accounting guidance did not distinguish between modifications which were substantive from modifications that were merely administrative. The accounting standards update requires entities to account for the effects of a modification unless the following three conditions are met: the fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified; the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; and the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. This update will be effective for annual and interim periods beginning after December 15, 2017. The adoption of this update did not have an impact on the Company’s financial statements. In March 2017, the FASB issued an update which shortens the amortization period for certain callable debt securities held at a premium to the earliest call date. Under current GAAP, entities amortize the premium as an adjustment of yield over the contractual life of the instrument even if the holder is certain that the call will be exercised. As a result, upon the exercise of a call on a callable debt security held at a premium, the unamortized premium is recorded as a loss in earnings. The update shortens the amortization period for certain callable debt securities held at a premium and requires the premium be amortized to the earliest call date. This update will be effective for annual and interim periods beginning after December 15, 2018. Entities are required to apply the amendments on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The adoption of this update is not expected to have a material impact on the Company’s financial statements. In March 2017, the FASB issued an update which changes the presentation of net periodic pension cost and net periodic postretirement benefit cost in a company’s income statement. The amendment requires that an employer report the service cost component in the same line item as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations, if one is presented. The amendment is effective for annual and interim periods beginning after December 15, 2017. Because the Company has minimal benefit plans that require the measurement of net periodic pension cost and net periodic post retirement benefit cost, the adoption of this update did not have an impact on the Company’s financial statements. In January 2017, the FASB issued an update to simplify the test for goodwill impairment. This amendment eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value. This update will be effective for the Company’s financial statements for annual years beginning after December 15, 2019. The adoption of this update is not expected to have a material impact on the Company’s financial statements. In January 2017, the FASB issued an update that clarifies the definition of a business as it pertains to business combinations. This amendment affects all companies and other reporting organizations that must determine whether they have sold or acquired a business. This update will be effective for the Company’s financial statements for fiscal years beginning after December 15, 2017. The adoption of this update did not have an impact on the Company’s financial statements. In September 2016, the FASB issued an accounting standards update to address diversity in presentation in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. This update will be effective for financial statements issued for fiscal years and interim periods beginning after December 15, 2017. The adoption of this update did not have an impact on the Company’s financial statements. In June 2016, the FASB issued an accounting standards update pertaining to the measurement of credit losses on financial instruments. This update requires the measurement of all expected credit losses for financial instruments held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. This update is intended to improve financial reporting by requiring timelier recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. This update will be effective for financial statements issued for fiscal years and interim periods beginning after December 15, 2019. The Company is currently evaluating its existing systems and data to support the new standard as well as assessing the impact that the guidance will have on the Company's consolidated financial statements. The Company has formed a working group under the direction of the chief risk officer that is comprised of individuals from the credit, risk management, finance and project management areas. The Company has been developing an implementation plan as well as considering various software providers and consultants to aid it in implementation. In early 2018, the Company contracted with a software and advisory service provider to aid in implementation. In February 2016, FASB issued accounting guidance that requires all lessees to recognize a lease liability and a right-of-use asset, measured at the present value of the future minimum lease payments, at the lease commencement date. Lessor accounting remains largely unchanged under the new guidance. The guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that reporting period, with early adoption permitted. A modified retrospective approach must be applied for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently assessing the impact of the new guidance on its consolidated financial statements by reviewing its existing lease contracts and service contracts that may include embedded leases. It is also considering various software providers to aid it in implementation. The Company expects to record an increase in assets and liabilities as a result of recognizing a right-of-use asset and a lease liability for its operating lease commitments. In January 2016, the FASB issued an accounting standards update intended to improve the recognition and measurement of financial instruments. Specifically, the accounting standards update requires all equity instruments, with the exception of those that are accounted for under the equity method of accounting, to be measured at fair value with changes in the fair value recognized through net income. Additionally, public business entities are required to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. The amendments in this update also require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. In February 2018, the FASB issued further guidance that provided technical corrections to this update. Those technical corrections included clarification on accounting for equity securities without a readily determinable fair value, remeasurement requirements on forward contracts and purchased options, and presentation requirements for certain fair value option liabilities. This amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. The adoption of this update required an adjustment on January 1, 2018 from other comprehensive income to retained earnings for the amount of the unrealized gain on equity securities as of December 31, 2017. Thereafter, any increases or decreases to the market value on these equity securities will be recorded through the consolidated statements of income. Please see the Consolidated Statement of Changes in Stockholders' Equity, Note 4-Investment Securities and Note 10-Comprehensive Income for more information. In May 2014, the FASB issued an accounting standards update that clarifies the principles for recognizing revenue. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to a customer in an amount that reflects the consideration to which the entity expects to be entitled in exchange for these goods or services. To achieve that core principle, an entity should apply the following steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. In 2016, the FASB issued further implementation guidance regarding revenue recognition. This additional guidance included clarification on certain principal versus agent considerations within the implementation of the guidance as well as clarification related to identifying performance obligations and licensing. The guidance also requires new qualitative and quantitative disclosures, including disaggregation of revenues and descriptions of performance obligations. The guidance along with its updates is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. In evaluating this standard, management has determined that the majority of revenue earned by the Company is from revenue streams not included in the scope of this standard. The Company has assessed its revenue streams and reviewed contracts potentially affected by the guidance including deposit related fees, interchange fees, investment commissions, merchant fee income and other noninterest income sources to determine the potential impact the new guidance is expected to have on the Company’s consolidated financial statements. The Company adopted the guidance on January 1, 2018 using the modified retrospective method. The Company did not have a cumulative-effect adjustment to opening retained earnings as a result of adopting this standard. Please see Note 2 - Revenue Recognition for more information.

In March 2018, the Financial Accounting Standards Board ("FASB") issued an update regarding the accounting implications of the recently issued Tax Cuts and Jobs Act (the "Tax Act"). The update clarifies that in a company's financial statements that include the reporting period in which the Tax Act was enacted, a company must first reflect the income tax effects of the Tax Act in which the accounting under U.S. GAAP is complete. Those amounts would not be provisional amounts. The company would also report provisional amounts for those specific income tax effects for which the accounting under U.S. GAAP will be incomplete but for which a reasonable estimate can be determined. If there are income tax effects for the Tax Act for which a reasonable estimate cannot be determined, the company would not report provisional amounts and would continue to apply U.S. GAAP based on the tax laws that were in effect immediately prior to the Tax Act being enacted. This accounting update is effective immediately. The Company believes its accounting for the the income tax effects of the Tax Act is complete. Technical corrections or other forthcoming guidance could change how we interpret provisions of the Tax Act, which may impact our effective tax rate and could affect our deferred tax assets, tax positions and/or our tax liabilities.

In February 2018, the FASB issued an update (ASU 2018-02) regarding the reclassification of certain tax effects from accumulated other comprehensive income. This update requires a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the newly enacted federal corporate tax rate. The amount of the reclassification would be the difference between the historical 35% corporate income tax rate and the newly enacted 21% corporate tax rate. This update eliminates the stranded tax effects associated with the change in the federal corporate income tax rate in the Tax Act and improves the usefulness of information reported to financial statement users. The amendments are effective for all entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption of the amendments is permitted including adoption in any interim period, for public business entities for reporting periods for which financial statements have not yet been issued and all other entities for reporting periods for which financial statements have not yet been made available for issuance. An entity may apply the amendments in the update retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized. The Company elected to adopt this update in December 2017, and recorded a $420,000 increase to retained earnings and reduction to accumulated other comprehensive income in December 2017.

In August 2017, the FASB issued an update intended to improve and simplify accounting rules around hedge accounting. Amendments expand and refine hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in this update also make certain targeted improvements to simplify the application of hedge accounting guidance and ease the administrative burden of hedge documentation requirements and assessing hedge effectiveness. This update will be effective for financial statements issued for fiscal years and interim periods beginning after December 15, 2019. The Company is still evaluating the impact that this guidance will have on its financial statements.

In July 2017, the FASB issued guidance which simplifies the accounting for certain financial instruments with down round features, a provision in an equity-linked financial instrument (or embedded feature) that provides a downward adjustment of the current exercise price based on the price of future equity offerings. The provisions of the new guidance related to down rounds are effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The adoption of this update is not expected to have a material impact on the Company’s financial statements because the Company does not have any equity-linked financial instruments that have such down round features.

In May 2017, the FASB issued an update which provides clarity and reduces diversity in practice when accounting for the modification of terms and conditions for share-based payment awards. Previous accounting guidance did not distinguish between modifications which were substantive from modifications that were merely administrative. The accounting standards update requires entities to account for the effects of a modification unless the following three conditions are met: the fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified; the vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; and the classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. This update will be effective for annual and interim periods beginning after December 15, 2017. The adoption of this update did not have an impact on the Company’s financial statements.

In March 2017, the FASB issued an update which shortens the amortization period for certain callable debt securities held at a premium to the earliest call date. Under current GAAP, entities amortize the premium as an adjustment of yield over the contractual life of the instrument even if the holder is certain that the call will be exercised. As a result, upon the exercise of a call on a callable debt security held at a premium, the unamortized premium is recorded as a loss in earnings. The update shortens the amortization period for certain callable debt securities held at a premium and requires the premium be amortized to the earliest call date. This update will be effective for annual and interim periods beginning after December 15, 2018. Entities are required to apply the amendments on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The adoption of this update is not expected to have a material impact on the Company’s financial statements.

In March 2017, the FASB issued an update which changes the presentation of net periodic pension cost and net periodic postretirement benefit cost in a company’s income statement. The amendment requires that an employer report the service cost component in the same line item as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations, if one is presented. The amendment is effective for annual and interim periods beginning after December 15, 2017. Because the Company has minimal benefit plans that require the measurement of net periodic pension cost and net periodic post retirement benefit cost, the adoption of this update did not have an impact on the Company’s financial statements.

In January 2017, the FASB issued an update to simplify the test for goodwill impairment. This amendment eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value. This update will be effective for the Company’s financial statements for annual years beginning after December 15, 2019. The adoption of this update is not expected to have a material impact on the Company’s financial statements.

In January 2017, the FASB issued an update that clarifies the definition of a business as it pertains to business combinations. This amendment affects all companies and other reporting organizations that must determine whether they have sold or acquired a business. This update will be effective for the Company’s financial statements for fiscal years beginning after December 15, 2017. The adoption of this update did not have an impact on the Company’s financial statements.

In September 2016, the FASB issued an accounting standards update to address diversity in presentation in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. This update will be effective for financial statements issued for fiscal years and interim periods beginning after December 15, 2017. The adoption of this update did not have an impact on the Company’s financial statements.

In June 2016, the FASB issued an accounting standards update pertaining to the measurement of credit losses on financial instruments. This update requires the measurement of all expected credit losses for financial instruments held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. This update is intended to improve financial reporting by requiring timelier recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. This update will be effective for financial statements issued for fiscal years and interim periods beginning after December 15, 2019. The Company is currently evaluating its existing systems and data to support the new standard as well as assessing the impact that the guidance will have on the Company's consolidated financial statements. The Company has formed a working group under the direction of the chief risk officer that is comprised of individuals from the credit, risk management, finance and project management areas. The Company has been developing an implementation plan as well as considering various software providers and consultants to aid it in implementation. In early 2018, the Company contracted with a software and advisory service provider to aid in implementation.

In February 2016, FASB issued accounting guidance that requires all lessees to recognize a lease liability and a right-of-use asset, measured at the present value of the future minimum lease payments, at the lease commencement date. Lessor accounting remains largely unchanged under the new guidance. The guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that reporting period, with early adoption permitted. A modified retrospective approach must be applied for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently assessing the impact of the new guidance on its consolidated financial statements by reviewing its existing lease contracts and service contracts that may include embedded leases. It is also considering various software providers to aid it in implementation. The Company expects to record an increase in assets and liabilities as a result of recognizing a right-of-use asset and a lease liability for its operating lease commitments.

In January 2016, the FASB issued an accounting standards update intended to improve the recognition and measurement of financial instruments. Specifically, the accounting standards update requires all equity instruments, with the exception of those that are accounted for under the equity method of accounting, to be measured at fair value with changes in the fair value recognized through net income. Additionally, public business entities are required to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. The amendments in this update also require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. In February 2018, the FASB issued further guidance that provided technical corrections to this update. Those technical corrections included clarification on accounting for equity securities without a readily determinable fair value, remeasurement requirements on forward contracts and purchased options, and presentation requirements for certain fair value option liabilities. This amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. The adoption of this update required an adjustment on January 1, 2018 from other comprehensive income to retained earnings for the amount of the unrealized gain on equity securities as of December 31, 2017. Thereafter, any increases or decreases to the market value on these equity securities will be recorded through the consolidated statements of income. Please see the Consolidated Statement of Changes in Stockholders' Equity, Note 4-Investment Securities and Note 10-Comprehensive Income for more information.

In May 2014, the FASB issued an accounting standards update that clarifies the principles for recognizing revenue. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to a customer in an amount that reflects the consideration to which the entity expects to be entitled in exchange for these goods or services. To achieve that core principle, an entity should apply the following steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. In 2016, the FASB issued further implementation guidance regarding revenue recognition. This additional guidance included clarification on certain principal versus agent considerations within the implementation of the guidance as well as clarification related to identifying performance obligations and licensing. The guidance also requires new qualitative and quantitative disclosures, including disaggregation of revenues and descriptions of performance obligations. The guidance along with its updates is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. In evaluating this standard, management has determined that the majority of revenue earned by the Company is from revenue streams not included in the scope of this standard. The Company has assessed its revenue streams and reviewed contracts potentially affected by the guidance including deposit related fees, interchange fees, investment commissions, merchant fee income and other noninterest income sources to determine the potential impact the new guidance is expected to have on the Company’s consolidated financial statements. The Company adopted the guidance on January 1, 2018 using the modified retrospective method. The Company did not have a cumulative-effect adjustment to opening retained earnings as a result of adopting this standard. Please see Note 2 - Revenue Recognition for more information.