Stockholders' Equity - Summary of Bank's Regulatory Capital Levels (Details) $ in Thousands	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)
Actual Amount
Total capital (to risk-weighted assets)	$ 748,323	$ 743,741
Tier 1 capital (to risk-weighted assets)	705,586	706,764
Common equity tier 1 capital (to risk-weighted assets)	705,586	706,764
Tier 1 capital (to adjusted total assets)	$ 705,586	$ 706,764
Actual Ratio
Total capital (to risk-weighted assets)	0.1537	0.1557
Tier 1 capital (to risk-weighted assets)	0.1449	0.1479
Common equity tier 1 capital (to risk-weighted assets)	0.1449	0.1479
Tier 1 capital (to adjusted total assets)	0.0923	0.0915
For Capital Adequacy Purposes Amount
Total capital (to risk-weighted assets)	$ 389,434	$ 382,247
Tier 1 capital (to risk-weighted assets)	292,076	286,685
Common equity tier 1 capital (to risk-weighted assets)	219,057	215,014
Tier 1 capital (to adjusted total assets)	$ 305,661	$ 309,031
For Capital Adequacy Purposes Ratio
Total capital (to risk-weighted assets)	0.0800	0.0800
Tier 1 capital (to risk-weighted assets)	0.0600	0.0600
Common equity tier 1 capital (to risk-weighted assets)	0.0450	0.0450
Tier 1 capital (to adjusted total assets)	0.0400	0.0400
Kearny Federal Savings Bank
Actual Amount
Total capital (to risk-weighted assets)	$ 704,969	$ 688,597
Tier 1 capital (to risk-weighted assets)	662,232	651,620
Common equity tier 1 capital (to risk-weighted assets)	662,232	651,620
Tier 1 capital (to adjusted total assets)	$ 662,232	$ 651,620
Actual Ratio
Total capital (to risk-weighted assets)	0.1449	0.1442
Tier 1 capital (to risk-weighted assets)	0.1361	0.1365
Common equity tier 1 capital (to risk-weighted assets)	0.1361	0.1365
Tier 1 capital (to adjusted total assets)	0.0868	0.0844
For Capital Adequacy Purposes Amount
Total capital (to risk-weighted assets)	$ 389,184	$ 382,034
Tier 1 capital (to risk-weighted assets)	291,888	286,525
Common equity tier 1 capital (to risk-weighted assets)	218,916	214,894
Tier 1 capital (to adjusted total assets)	$ 305,162	$ 308,656
For Capital Adequacy Purposes Ratio
Total capital (to risk-weighted assets)	0.0800	0.0800
Tier 1 capital (to risk-weighted assets)	0.0600	0.0600
Common equity tier 1 capital (to risk-weighted assets)	0.0450	0.0450
Tier 1 capital (to adjusted total assets)	0.0400	0.0400
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount
Total capital (to risk-weighted assets)	$ 486,481	$ 477,542
Tier 1 capital (to risk-weighted assets)	389,184	382,034
Common equity tier 1 capital (to risk-weighted assets)	316,212	310,402
Tier 1 capital (to adjusted total assets)	$ 381,453	$ 385,820
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio
Total capital (to risk-weighted assets)	0.1000	0.1000
Tier 1 capital (to risk-weighted assets)	0.0800	0.0800
Common equity tier 1 capital (to risk-weighted assets)	0.0650	0.0650
Tier 1 capital (to adjusted total assets)	5.00%	5.00%

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
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