0002115119 2026-01-01 2026-03-31 0002115119 2026-03-31 shares 0002115119 --12-31 2026-03-31 2026 Q1 false 10-Q true false 333-294103 Columbia Financial, Inc. MD 42-1991301 19-01 Route 208 North Fair Lawn NJ 07410 800 522-4167 None No Yes Accelerated Filer false false false 100