v3.26.1
Regulatory Capital - Summary of the Bank's Compliance (Details)
$ in Thousands
Mar. 31, 2026
USD ($)
Dec. 31, 2025
USD ($)
Savings bank    
Tier I (leverage) capital:    
Tier I (leverage) capital, capital level, amount $ 921,751 $ 909,636
Tier I (leverage) capital, capital level, percent 0.1045 0.1029
Tier I (leverage) capital, requirement to be well-capitalized, amount $ 440,854 $ 441,813
Tier I (leverage) capital, requirement to be well-capitalized, percent 0.05 0.05
Tier I (leverage) capital, excess capital, amount $ 480,897 $ 467,823
Tier I (leverage) capital, excess capital, percent 0.0545 0.0529
Common Equity Tier I risk-based capital:    
Common Equity Tier 1 Risk-Based Capital, Amount $ 921,751 $ 909,636
Common Equity Tier 1 Risk-Based Capital, Percent 0.1389 0.1373
Common Equity Tier 1 Risk-Based Capital, Well Capitalized, Amount $ 431,199 $ 430,567
Common Equity Tier 1 Risk-Based Capital, Well Capitalized, Percent 0.065% 0.065%
Common Equity Tier I risk-based capital, excess, Amount $ 490,552 $ 479,069
Common Equity Tier I risk-based capital, excess, Percent 0.0739% 0.0723%
Tier I risk-based capital:    
Tier 1 Risk-Based Capital, Capital level, Amount $ 921,751 $ 909,636
Tier 1 Risk-Based Capital, Capital level, Percent 0.1389 0.1373
Tier 1 Risk-Based Capital, Well Capitalized, Amount $ 530,706 $ 529,929
Tier 1 Risk-Based Capital, Well Capitalized, Percent 0.08 0.08
Tier 1 Risk-Based Capital, Excess Capital, Amount $ 391,045 $ 379,707
Tier 1 Risk-Based Capital, Excess Capital, Percent 0.0589 0.0573
Total risk-based capital:    
Total risk-based, Capital level, Amount $ 967,947 $ 954,061
Total risk-based, Capital level, Percent 0.1459 0.144
Total risk-based Capital, Well Capitalized, Amount $ 663,383 $ 662,411
Total risk-based Capital, Well Capitalized, Percent 0.10 0.10
Total risk-based Capital, Excess, Amount $ 304,564 $ 291,650
Total risk-based Capital, Excess, Percent 0.0459 0.044
Holding company    
Tier I (leverage) capital:    
Tier I (leverage) capital, capital level, amount $ 747,808 $ 752,523
Tier I (leverage) capital, capital level, percent 0.0848 0.0852
Tier I (leverage) capital, requirement to be well-capitalized, amount $ 440,855 $ 441,788
Tier I (leverage) capital, requirement to be well-capitalized, percent 0.05 0.05
Tier I (leverage) capital, excess capital, amount $ 306,953 $ 310,735
Tier I (leverage) capital, excess capital, percent 0.0348 0.0352
Common Equity Tier I risk-based capital:    
Common Equity Tier 1 Risk-Based Capital, Amount $ 694,708 $ 702,747
Common Equity Tier 1 Risk-Based Capital, Percent 0.1047 0.1061
Common Equity Tier 1 Risk-Based Capital, Well Capitalized, Amount $ 431,258 $ 430,555
Common Equity Tier 1 Risk-Based Capital, Well Capitalized, Percent 0.065% 0.065%
Common Equity Tier I risk-based capital, excess, Amount $ 263,450 $ 272,192
Common Equity Tier I risk-based capital, excess, Percent 0.0397% 0.0411%
Tier I risk-based capital:    
Tier 1 Risk-Based Capital, Capital level, Amount $ 747,808 $ 752,523
Tier 1 Risk-Based Capital, Capital level, Percent 0.1127 0.1136
Tier 1 Risk-Based Capital, Well Capitalized, Amount $ 530,779 $ 529,914
Tier 1 Risk-Based Capital, Well Capitalized, Percent 0.08 0.08
Tier 1 Risk-Based Capital, Excess Capital, Amount $ 217,029 $ 222,609
Tier 1 Risk-Based Capital, Excess Capital, Percent 0.0327 0.0336
Total risk-based capital:    
Total risk-based, Capital level, Amount $ 984,004 $ 986,948
Total risk-based, Capital level, Percent 0.1483 0.149
Total risk-based Capital, Well Capitalized, Amount $ 663,474 $ 662,392
Total risk-based Capital, Well Capitalized, Percent 0.10 0.10
Total risk-based Capital, Excess, Amount $ 320,530 $ 324,556
Total risk-based Capital, Excess, Percent 0.0483 0.049