Loans Receivable, Allowance for Credit Losses and Credit Quality (Details) - USD ($)	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Loans Receivable, Allowance for Credit Losses and Credit Quality
Loans held for sale, at fair value	$ 63,971,000		$ 66,447,000
Peer group financial institution size	10,000,000,000
Allowances for credit losses individual impairment threshold amount	$ 500,000
Loans to value percentage, excluded from individually evaluated loans	60.00%
Total loans	$ 6,220,265,000		$ 5,994,016,000
Total loans (in percentage)	100.00%		100.00%
Deferred fees, net	$ (10,355,000)		$ (7,876,000)
Allowance for credit losses	(80,195,000)	$ (38,338,000)	(87,411,000)	$ (38,744,000)
Net loans	6,129,715,000		5,898,729,000
Cannabis industry
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	466,800,000		404,800,000
Mortgage backed securities \| Cannabis industry
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	321,000,000		228,800,000
Residential real estate, portfolio
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 1,341,318,000		$ 1,329,758,000
Total loans (in percentage)	21.56%		22.19%
Residential real estate, portfolio \| One to four-family residential
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 1,185,601,000		$ 1,177,156,000
Total loans (in percentage)	19.06%		19.64%
Allowance for credit losses	$ (1,709,000)	(1,293,000)	$ (1,703,000)	(1,195,000)
Residential real estate, portfolio \| Home equity
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 155,717,000		$ 152,602,000
Total loans (in percentage)	2.50%		2.55%
Allowance for credit losses	$ (155,000)	(88,000)	$ (152,000)	(74,000)
Commercial real estate and Commercial, portfolio
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 4,388,833,000		$ 4,179,812,000
Total loans (in percentage)	70.56%		69.72%
Commercial real estate, portfolio
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 2,463,026,000		$ 2,441,570,000
Total loans (in percentage)	39.60%		40.72%
Commercial real estate, portfolio \| Multi-family residential
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 538,164,000		$ 517,527,000
Total loans (in percentage)	8.65%		8.63%
Allowance for credit losses	$ (1,397,000)	(615,000)	$ (1,188,000)	(599,000)
Commercial real estate, portfolio \| Commercial real estate
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 1,924,862,000		$ 1,924,043,000
Total loans (in percentage)	30.95%		32.09%
Allowance for credit losses	$ (21,985,000)	(8,758,000)	$ (21,599,000)	(9,481,000)
Commercial, portfolio \| Construction & Land Development
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 782,721,000		$ 730,573,000
Total loans (in percentage)	12.58%		12.19%
Allowance for credit losses	$ (5,204,000)	(4,840,000)	$ (5,050,000)	(4,137,000)
Commercial, portfolio \| Commercial and industrial
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 1,143,086,000		$ 1,007,669,000
Total loans (in percentage)	18.38%		16.81%
Allowance for credit losses	$ (41,334,000)	(12,087,000)	$ (49,599,000)	(11,174,000)
Consumer, portfolio
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 212,923,000		$ 203,497,000
Total loans (in percentage)	3.42%		3.40%
Allowance for credit losses	$ (8,189,000)	(10,657,000)	$ (7,895,000)	$ (12,084,000)
Loans purchased	14,700,000	$ 14,400,000
Mortgage warehouse, portfolio
Loans Receivable, Allowance for Credit Losses and Credit Quality
Total loans	$ 277,191,000		$ 280,949,000
Total loans (in percentage)	4.46%		4.69%
Allowance for credit losses	$ (222,000)		$ (225,000)

NB Bancorp, Inc. 10-Q