Summary of Significant Accounting Policies (Policies)	6 Months Ended
Dec. 31, 2020
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The unaudited consolidated financial statements include the accounts of Kearny Financial Corp. (the “Company”), its wholly-owned subsidiary, Kearny Bank (the “Bank”) and the Bank’s wholly-owned subsidiaries, CJB Investment Corp., KFS Insurance Services, Inc. and Millington Savings Service Corp. The Company conducts its business principally through the Bank. Management prepared the unaudited consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”), including the elimination of all significant inter-company accounts and transactions during consolidation.
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements were prepared in accordance with instructions for Form 10-Q and Regulation S-X and do not include information or footnotes necessary for a complete presentation of financial condition, income, comprehensive (loss) income, changes in stockholders’ equity and cash flows in conformity with GAAP. However, in the opinion of management, all adjustments (consisting of normal recurring adjustments) necessary for a fair presentation of the unaudited consolidated financial statements have been included. The results of operations for the three-month and six-month periods ended December 31, 2020 are not necessarily indicative of the results that may be expected for the entire fiscal year or any other period. The data in the consolidated statement of financial condition for June 30, 2020 was derived from the Company’s 2020 Annual Report on Form 10-K. That data, along with the interim unaudited financial information presented in the consolidated statements of financial condition, income, comprehensive income, changes in stockholders’ equity and cash flows should be read in conjunction with the audited consolidated financial statements, including the notes thereto, included in the Company’s 2020 Annual Report on Form 10-K.
Risk and Uncertainties	Risks and Uncertainties As previously disclosed, on March 11, 2020, the World Health Organization declared the outbreak of COVID-19 a global pandemic. The COVID-19 pandemic has adversely affected, and may continue to adversely affect, local, national and global economic activity. The spread of the outbreak has caused significant disruptions to the U.S. economy, significant reductions in the targeted federal funds rate and has disrupted banking and other financial activity in the areas in which the Company operates. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was enacted to, among other provisions, provide emergency assistance for individuals, families and businesses affected by the COVID-19 pandemic. On December 27, 2020 the 2021 Consolidated Appropriations Act, was enacted as part of an omnibus spending bill for the 2021 federal fiscal year, included provisions intended to provide additional aid to those impacted by the pandemic. Reductions in interest rates and other effects of the COVID-19 pandemic may continue to materially and adversely affect the Company's financial condition and results of operations in future periods. It is unknown how long the adverse conditions associated with the COVID-19 pandemic will last and what the complete financial effect will be to the Company. It is possible that estimates made in the financial statements could be materially and adversely impacted as a result of these conditions, including estimates regarding expected credit losses on loans receivable, impairment of investment securities and impairment of goodwill. Although the Company continues to operate while taking steps to ensure the safety of employees and clients, COVID-19 could also potentially create widespread business continuity issues for the Company. The extent to which the COVID-19 pandemic will continue to impact the Company’s business, financial condition and results of operations in future periods will depend on future developments, including the scope and duration of the pandemic, the efficacy and adoption of COVID-19 vaccines and actions taken by governmental authorities and other third parties in response to the pandemic, as well as further actions the Company may take as may be required by government authorities or that the Company determines is in the best interests of its employees and clients. There is no certainty that such measures will be sufficient to mitigate the risks posed by the pandemic.
Adoption of New Accounting Standards	Adoption of New Accounting Standards On July 1, 2020, the Company adopted ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”, which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (CECL) methodology. The Company adopted ASU 2016-13 using a modified retrospective approach. Results for reporting periods beginning after July 1, 2020 are presented under Topic 326, while prior period amounts continue to be reported in accordance with previously applicable GAAP. At adoption, the Company increased its allowance for credit losses by $20.2 million, comprised of $19.6 million for loans receivable and $536,000 for unfunded commitments. Upon adoption the Company recorded a cumulative effect adjustment that reduced stockholders’ equity by $14.2 million, net of tax.
Allowance for Credit Losses	Allowance for Credit Losses The allowance for credit losses represents the estimated amount considered necessary to cover lifetime expected credit losses inherent in financial assets at the balance sheet date. The measurement of expected credit losses is applicable to loans receivable and securities measured at amortized cost. It also applies to off-balance sheet credit exposures such as loan commitments and unused lines of credit. The allowance is established through a provision for credit losses that is charged against income. The methodology for determining the allowance for credit losses is considered a critical accounting policy by management because of the high degree of judgment involved, the subjectivity of the assumptions used, and the potential for changes in the forecasted economic environment that could result in changes to the amount of the recorded allowance for credit losses. The allowance for credit losses is reported separately as a contra-asset on the consolidated statement of financial condition. The expected credit loss for unfunded lending commitments and unfunded loan commitments is reported on the Consolidated Statement of Financial Condition in other liabilities while the provision for credit losses related to unfunded commitments is reported in other non-interest expense. Allowance for Credit Losses on Loans Receivable The allowance for credit losses on loans is deducted from the amortized cost basis of the loan to present the net amount expected to be collected. Expected losses are evaluated and calculated on a collective, or pooled, basis for those loans which share similar risk characteristics. At each reporting period, the Company evaluates whether loans within a pool continue to exhibit similar risk characteristics. If the risk characteristics of a loan change, such that they are no longer similar to other loans in the pool, the Company will evaluate the loan with a different pool of loans that share similar risk characteristics. If the loan does not share risk characteristics with other loans, the Company will evaluate the loan on an individual basis. The Company evaluates the pooling methodology at least annually. Loans are charged off against the allowance for credit losses when the Company believes the balances to be uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged off or expected to be charged off. The Company has chosen to segment its portfolio consistent with the manner in which it manages credit risk. Such segments include multi-family, nonresidential mortgage, commercial business, construction, one- to four-family residential, home equity and consumer. For most segments the Company calculates estimated credit losses using a probability of default and loss given default methodology, the results of which are applied to the aggregated discounted cash flow of each individual loan within the segment. The point in time probability of default and loss given default are then conditioned by macroeconomic scenarios to incorporate reasonable and supportable forecasts that affect the collectability of the reported amount. The Company estimates the allowance for credit losses on loans via a quantitative analysis which considers relevant available information from internal and external sources related to past events and current conditions, as well as the incorporation of reasonable and supportable forecasts. The Company evaluates a variety of factors including third party economic forecasts, industry trends and other available published economic information in arriving at its forecasts. After the reasonable and supportable forecast period, the Company reverts, on a straight-line basis, to average historical losses. Expected credit losses are estimated over the contractual term of the loans, adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals, and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower or the renewal option is included in the original or modified contract at the reporting date and are not unconditionally cancelable by the Company. Also included in the allowance for credit losses on loans are qualitative reserves to cover losses that are expected but, in the Company’s assessment, may not be adequately represented in the quantitative analysis or the forecasts described above. Factors that the Company considers include changes in lending policies and procedures, business conditions, the nature and size of the portfolio, portfolio concentrations, the volume and severity of past due loans and non-accrual loans, the effect of external factors such as competition, legal and regulatory requirements, among others. Furthermore, the Company considers the inherent uncertainty in quantitative models that are built upon historical data. Individually Evaluated Loans On a case-by-case basis, the Company may conclude that a loan should be evaluated on an individual basis based on its disparate risk characteristics. When the Company determines that a loan no longer shares similar risk characteristics with other loans in the portfolio, the allowance will be determined on an individual basis using the present value of expected cash flows or, for collateral-dependent loans, the fair value of the collateral as of the reporting date, less estimated selling costs, as applicable. If the fair value of the collateral is less than the amortized cost basis of the loan, the Company will charge off the difference between the fair value of the collateral, less costs to sell at the reporting date and the amortized cost basis of the loan. Acquired Loans Acquired loans are included in the Company's calculation of the allowance for credit losses. How the allowance on an acquired loan is recorded depends on whether or not it has been classified as a Purchased Credit Deteriorated (“PCD”) loan. PCD loans are loans acquired at a discount that is due, in part, to credit quality. PCD loans are accounted for in accordance with ASC Subtopic 326-20 and are initially recorded at fair value as determined by the sum of the present value of expected future cash flows and an allowance for credit losses at acquisition. The allowance for PCD loans is recorded through a gross-up effect, while the allowance for acquired non-PCD loans is recorded through provision expense, consistent with originated loans. Thus, the determination of which loans are PCD and non-PCD can have a significant impact on the accounting for these loans. Subsequent to acquisition, the allowance for PCD loans will generally follow the same estimation, provision and charge-off process as non-PCD acquired and originated loans. Allowance for Credit Losses on Off-Balance Sheet Commitments The Company is required to include unfunded commitments that are expected to be funded in the future within the allowance calculation, other than those that are unconditionally cancelable. To arrive at that reserve, the reserve percentage for each applicable segment is applied to the unused portion of the expected commitment balance and is multiplied by the expected funding rate. To determine the expected funding rate, the Company uses a historical utilization rate for each segment. As noted above, the allowance for credit losses on unfunded loan commitments is included in other liabilities on the consolidated statement of financial condition and the related credit expense is recorded in other non-interest expense in the consolidated statements of income. Allowance for Credit Losses on Held to Maturity Securities The Company’s entire portfolio of held to maturity securities consists of municipal bonds which are highly rated by major rating agencies and have a long history of no credit losses. In estimating the net amount expected to be collected for held to maturity securities in an unrealized loss position, a historical loss based method is utilized. Allowance for Credit Losses on Available for Sale Securities For available for sale securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more than likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For securities available for sale that do not meet the above criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, the Company considers the extent to which fair value is less than amortized cost, any changes to the rating by a rating agency, and adverse conditions related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of the cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income, net of tax. The Company elected the practical expedient of zero loss estimates for securities issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government, are highly rate by major agencies and have a long history of no credit losses. Changes in the allowance for credit losses are recorded as provision for, or reversal of, credit loss expense. Losses are charged against the allowance when management believes the uncollectibility of an available for sale security is confirmed or when either of the criteria regarding intent or requirement to sell is met. Accrued Interest Receivable The Company made an accounting policy election to exclude accrued interest receivable from the amortized cost basis of loans, available for sale securities, and held to maturity securities. Accrued interest receivable on loans is reported as a component of accrued interest receivable on the Consolidated Statement of Financial Condition, totaled $15.5 million at December 31, 2020 and is excluded from the estimate of credit losses. Accrued interest receivable on available of sale securities and held to maturity securities, also a component of accrued interest receivable on the Consolidated Statement of Financial Condition, totaled $4.1 million and $202,000, respectively, at December 31, 2020 and is excluded from the estimate of credit losses. There were no material accrued interest balances for loans on deferral under the CARES Act.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Dec. 31, 2020

The unaudited consolidated financial statements include the accounts of Kearny Financial Corp. (the “Company”), its wholly-owned subsidiary, Kearny Bank (the “Bank”) and the Bank’s wholly-owned subsidiaries, CJB Investment Corp., KFS Insurance Services, Inc. and Millington Savings Service Corp. The Company conducts its business principally through the Bank. Management prepared the unaudited consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”), including the elimination of all significant inter-company accounts and transactions during consolidation.

Basis of Presentation

The accompanying unaudited consolidated financial statements were prepared in accordance with instructions for Form 10-Q and Regulation S-X and do not include information or footnotes necessary for a complete presentation of financial condition, income, comprehensive (loss) income, changes in stockholders’ equity and cash flows in conformity with GAAP. However, in the opinion of management, all adjustments (consisting of normal recurring adjustments) necessary for a fair presentation of the unaudited consolidated financial statements have been included. The results of operations for the three-month and six-month periods ended December 31, 2020 are not necessarily indicative of the results that may be expected for the entire fiscal year or any other period.

The data in the consolidated statement of financial condition for June 30, 2020 was derived from the Company’s 2020 Annual Report on Form 10-K. That data, along with the interim unaudited financial information presented in the consolidated statements of financial condition, income, comprehensive income, changes in stockholders’ equity and cash flows should be read in conjunction with the audited consolidated financial statements, including the notes thereto, included in the Company’s 2020 Annual Report on Form 10-K.

Risk and Uncertainties

Risks and Uncertainties

As previously disclosed, on March 11, 2020, the World Health Organization declared the outbreak of COVID-19 a global pandemic. The COVID-19 pandemic has adversely affected, and may continue to adversely affect, local, national and global economic activity. The spread of the outbreak has caused significant disruptions to the U.S. economy, significant reductions in the targeted federal funds rate and has disrupted banking and other financial activity in the areas in which the Company operates. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was enacted to, among other provisions, provide emergency assistance for individuals, families and businesses affected by the COVID-19 pandemic. On December 27, 2020 the 2021 Consolidated Appropriations Act, was enacted as part of an omnibus spending bill for the 2021 federal fiscal year, included provisions intended to provide additional aid to those impacted by the pandemic.

Reductions in interest rates and other effects of the COVID-19 pandemic may continue to materially and adversely affect the Company's financial condition and results of operations in future periods. It is unknown how long the adverse conditions associated with the COVID-19 pandemic will last and what the complete financial effect will be to the Company. It is possible that estimates made in the financial statements could be materially and adversely impacted as a result of these conditions, including estimates regarding expected credit losses on loans receivable, impairment of investment securities and impairment of goodwill. Although the Company continues to operate while taking steps to ensure the safety of employees and clients, COVID-19 could also potentially create widespread business continuity issues for the Company.

The extent to which the COVID-19 pandemic will continue to impact the Company’s business, financial condition and results of operations in future periods will depend on future developments, including the scope and duration of the pandemic, the efficacy and adoption of COVID-19 vaccines and actions taken by governmental authorities and other third parties in response to the pandemic, as well as further actions the Company may take as may be required by government authorities or that the Company determines is in the best interests of its employees and clients. There is no certainty that such measures will be sufficient to mitigate the risks posed by the pandemic.

Adoption of New Accounting Standards

On July 1, 2020, the Company adopted ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”, which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (CECL) methodology. The Company adopted ASU 2016-13 using a modified retrospective approach. Results for reporting periods beginning after July 1, 2020 are presented under Topic 326, while prior period amounts continue to be reported in accordance with previously applicable GAAP. At adoption, the Company increased its allowance for credit losses by $20.2 million, comprised of $19.6 million for loans receivable and $536,000 for unfunded commitments. Upon adoption the Company recorded a cumulative effect adjustment that reduced stockholders’ equity by $14.2 million, net of tax.

Allowance for Credit Losses

The allowance for credit losses represents the estimated amount considered necessary to cover lifetime expected credit losses inherent in financial assets at the balance sheet date. The measurement of expected credit losses is applicable to loans receivable and securities measured at amortized cost. It also applies to off-balance sheet credit exposures such as loan commitments and unused lines of credit. The allowance is established through a provision for credit losses that is charged against income. The methodology for determining the allowance for credit losses is considered a critical accounting policy by management because of the high degree of judgment involved, the subjectivity of the assumptions used, and the potential for changes in the forecasted economic environment that could result in changes to the amount of the recorded allowance for credit losses. The allowance for credit losses is reported separately as a contra-asset on the consolidated statement of financial condition. The expected credit loss for unfunded lending commitments and unfunded loan commitments is reported on the Consolidated Statement of Financial Condition in other liabilities while the provision for credit losses related to unfunded commitments is reported in other non-interest expense.

Allowance for Credit Losses on Loans Receivable

The allowance for credit losses on loans is deducted from the amortized cost basis of the loan to present the net amount expected to be collected. Expected losses are evaluated and calculated on a collective, or pooled, basis for those loans which share similar risk characteristics. At each reporting period, the Company evaluates whether loans within a pool continue to exhibit similar risk characteristics. If the risk characteristics of a loan change, such that they are no longer similar to other loans in the pool, the Company will evaluate the loan with a different pool of loans that share similar risk characteristics. If the loan does not share risk characteristics with other loans, the Company will evaluate the loan on an individual basis. The Company evaluates the pooling methodology at least annually. Loans are charged off against the allowance for credit losses when the Company believes the balances to be uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged off or expected to be charged off.

The Company has chosen to segment its portfolio consistent with the manner in which it manages credit risk. Such segments include multi-family, nonresidential mortgage, commercial business, construction, one- to four-family residential, home equity and consumer. For most segments the Company calculates estimated credit losses using a probability of default and loss given default methodology, the results of which are applied to the aggregated discounted cash flow of each individual loan within the segment. The point in time probability of default and loss given default are then conditioned by macroeconomic scenarios to incorporate reasonable and supportable forecasts that affect the collectability of the reported amount.

The Company estimates the allowance for credit losses on loans via a quantitative analysis which considers relevant available information from internal and external sources related to past events and current conditions, as well as the incorporation of reasonable and supportable forecasts. The Company evaluates a variety of factors including third party economic forecasts, industry trends and other available published economic information in arriving at its forecasts. After the reasonable and supportable forecast period, the Company reverts, on a straight-line basis, to average historical losses. Expected credit losses are estimated over the contractual term of the loans, adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals, and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower or the renewal option is included in the original or modified contract at the reporting date and are not unconditionally cancelable by the Company.

Also included in the allowance for credit losses on loans are qualitative reserves to cover losses that are expected but, in the Company’s assessment, may not be adequately represented in the quantitative analysis or the forecasts described above. Factors that the Company considers include changes in lending policies and procedures, business conditions, the nature and size of the portfolio, portfolio concentrations, the volume and severity of past due loans and non-accrual loans, the effect of external factors such as competition, legal and regulatory requirements, among others. Furthermore, the Company considers the inherent uncertainty in quantitative models that are built upon historical data.

Individually Evaluated Loans

On a case-by-case basis, the Company may conclude that a loan should be evaluated on an individual basis based on its disparate risk characteristics. When the Company determines that a loan no longer shares similar risk characteristics with other loans in the portfolio, the allowance will be determined on an individual basis using the present value of expected cash flows or, for collateral-dependent loans, the fair value of the collateral as of the reporting date, less estimated selling costs, as applicable. If the fair value of the collateral is less than the amortized cost basis of the loan, the Company will charge off the difference between the fair value of the collateral, less costs to sell at the reporting date and the amortized cost basis of the loan.

Acquired Loans

Acquired loans are included in the Company's calculation of the allowance for credit losses. How the allowance on an acquired loan is recorded depends on whether or not it has been classified as a Purchased Credit Deteriorated (“PCD”) loan. PCD loans are loans acquired at a discount that is due, in part, to credit quality. PCD loans are accounted for in accordance with ASC Subtopic 326-20 and are initially recorded at fair value as determined by the sum of the present value of expected future cash flows and an allowance for credit losses at acquisition. The allowance for PCD loans is recorded through a gross-up effect, while the allowance for acquired non-PCD loans is recorded through provision expense, consistent with originated loans. Thus, the determination of which loans are PCD and non-PCD can have a significant impact on the accounting for these loans. Subsequent to acquisition, the allowance for PCD loans will generally follow the same estimation, provision and charge-off process as non-PCD acquired and originated loans.

Allowance for Credit Losses on Off-Balance Sheet Commitments

The Company is required to include unfunded commitments that are expected to be funded in the future within the allowance calculation, other than those that are unconditionally cancelable. To arrive at that reserve, the reserve percentage for each applicable segment is applied to the unused portion of the expected commitment balance and is multiplied by the expected funding rate. To determine the expected funding rate, the Company uses a historical utilization rate for each segment. As noted above, the allowance for credit losses on unfunded loan commitments is included in other liabilities on the consolidated statement of financial condition and the related credit expense is recorded in other non-interest expense in the consolidated statements of income.

Allowance for Credit Losses on Held to Maturity Securities

The Company’s entire portfolio of held to maturity securities consists of municipal bonds which are highly rated by major rating agencies and have a long history of no credit losses. In estimating the net amount expected to be collected for held to maturity securities in an unrealized loss position, a historical loss based method is utilized.

Allowance for Credit Losses on Available for Sale Securities

For available for sale securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more than likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For securities available for sale that do not meet the above criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, the Company considers the extent to which fair value is less than amortized cost, any changes to the rating by a rating agency, and adverse conditions related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of the cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income, net of tax. The Company elected the practical expedient of zero loss estimates for securities issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government, are highly rate by major agencies and have a long history of no credit losses.

Changes in the allowance for credit losses are recorded as provision for, or reversal of, credit loss expense. Losses are charged against the allowance when management believes the uncollectibility of an available for sale security is confirmed or when either of the criteria regarding intent or requirement to sell is met.

Accrued Interest Receivable

The Company made an accounting policy election to exclude accrued interest receivable from the amortized cost basis of loans, available for sale securities, and held to maturity securities. Accrued interest receivable on loans is reported as a component of accrued interest receivable on the Consolidated Statement of Financial Condition, totaled $15.5 million at December 31, 2020 and is excluded from the estimate of credit losses. Accrued interest receivable on available of sale securities and held to maturity securities, also a component of accrued interest receivable on the Consolidated Statement of Financial Condition, totaled $4.1 million and $202,000, respectively, at December 31, 2020 and is excluded from the estimate of credit losses. There were no material accrued interest balances for loans on deferral under the CARES Act.