Loans and Allowance for Credit Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Past Due [Line Items]
Total	$ 7,959,382	$ 8,071,957
Nonaccrual	49,949	55,558	$ 27,937
Current
Financing Receivable, Past Due [Line Items]
Total	7,888,274	8,003,815
Total Past Due Loans
Financing Receivable, Past Due [Line Items]
Total	71,108	68,142
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	19,812	5,195
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,347	7,389
Commercial loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,836,088	2,921,761
Nonaccrual	15,125	15,185	3,228
Commercial loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,321,544	1,330,605
Nonaccrual	17,909	24,906	11,173
Commercial loans | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	391,584	365,377
Nonaccrual	869	869	0
Commercial loans | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,299,414	1,315,863
Nonaccrual	5,332	3,576	2,988
Commercial loans | Current | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	2,815,134	2,906,576
Commercial loans | Current | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	1,297,254	1,305,388
Commercial loans | Current | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	390,715	364,508
Commercial loans | Current | Business banking
Financing Receivable, Past Due [Line Items]
Total	1,291,395	1,308,368
Commercial loans | Total Past Due Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	20,954	15,185
Commercial loans | Total Past Due Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	24,290	25,217
Commercial loans | Total Past Due Loans | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	869	869
Commercial loans | Total Past Due Loans | Business banking
Financing Receivable, Past Due [Line Items]
Total	8,019	7,495
Commercial loans | 30-59 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	5,829	0
Commercial loans | 30-59 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	6,381	311
Commercial loans | 30-59 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial loans | 30-59 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	2,167	999
Commercial loans | 60-89 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial loans | 60-89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial loans | 60-89 Days Past Due | Commercial construction
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial loans | 60-89 Days Past Due | Business banking
Financing Receivable, Past Due [Line Items]
Total	520	2,920
Consumer loans | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	2,026,801	2,047,071
Nonaccrual	10,573	10,864	10,318
Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Total	83,951	91,280
Nonaccrual	141	158	$ 230
Consumer loans | Current | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	2,010,816	2,028,472
Consumer loans | Current | Other consumer
Financing Receivable, Past Due [Line Items]
Total	82,960	90,503
Consumer loans | Total Past Due Loans | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	15,985	18,599
Consumer loans | Total Past Due Loans | Other consumer
Financing Receivable, Past Due [Line Items]
Total	991	777
Consumer loans | 30-59 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	4,601	3,281
Consumer loans | 30-59 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	834	604
Consumer loans | 60-89 Days Past Due | Consumer real estate
Financing Receivable, Past Due [Line Items]
Total	811	4,454
Consumer loans | 60-89 Days Past Due | Other consumer
Financing Receivable, Past Due [Line Items]
Total	$ 16	$ 15