Loans Receivable - Composition of Impaired Loans by Portfolio Segment and Class of Financing Receivable (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		$ 94,384,000	$ 81,236,000
Nonaccrual loans with an allowance	$ 78,970,000	78,970,000	68,835,000
Nonaccrual loans with no allowance	23,189,000	23,189,000	25,549,000
Nonaccrual loans at ending balance	102,159,000	102,159,000	94,384,000
Loans 90 days past due and accruing	2,511,000	2,511,000	2,698,000
Interest income, accrual method	0	0	0
Amortized cost basis of collateral-dependent loans	77,254,000	77,254,000	67,084,000
Real estate
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	70,707,000	70,707,000	67,084,000
Equipment
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	6,547,000	6,547,000
Personal Banking
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		18,264,000	15,746,000
Nonaccrual loans with an allowance	13,552,000	13,552,000	16,804,000
Nonaccrual loans with no allowance	1,515,000	1,515,000	1,460,000
Nonaccrual loans at ending balance	15,067,000	15,067,000	18,264,000
Loans 90 days past due and accruing	2,002,000	2,002,000	2,463,000
Personal Banking | Residential mortgage loans
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		8,727,000	7,574,000
Nonaccrual loans with an allowance	5,803,000	5,803,000	8,304,000
Nonaccrual loans with no allowance	600,000	600,000	423,000
Nonaccrual loans at ending balance	6,403,000	6,403,000	8,727,000
Loans 90 days past due and accruing	1,390,000	1,390,000	1,671,000
Personal Banking | Home equity loans
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		4,492,000	4,145,000
Nonaccrual loans with an allowance	3,907,000	3,907,000	4,084,000
Nonaccrual loans with no allowance	148,000	148,000	408,000
Nonaccrual loans at ending balance	4,055,000	4,055,000	4,492,000
Loans 90 days past due and accruing	34,000	34,000	26,000
Personal Banking | Vehicle loans
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		4,816,000	3,771,000
Nonaccrual loans with an allowance	3,585,000	3,585,000	4,187,000
Nonaccrual loans with no allowance	757,000	757,000	629,000
Nonaccrual loans at ending balance	4,342,000	4,342,000	4,816,000
Loans 90 days past due and accruing	8,000	8,000	44,000
Personal Banking | Consumer loans
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		229,000	256,000
Nonaccrual loans with an allowance	257,000	257,000	229,000
Nonaccrual loans with no allowance	10,000	10,000	0
Nonaccrual loans at ending balance	267,000	267,000	229,000
Loans 90 days past due and accruing	570,000	570,000	722,000
Commercial Banking
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		76,120,000	65,490,000
Nonaccrual loans with an allowance	65,418,000	65,418,000	52,031,000
Nonaccrual loans with no allowance	21,674,000	21,674,000	24,089,000
Nonaccrual loans at ending balance	87,092,000	87,092,000	76,120,000
Loans 90 days past due and accruing	509,000	509,000	235,000
Amortized cost basis of collateral-dependent loans	77,254,000	77,254,000	67,084,000
Commercial Banking | Real estate
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	70,707,000	70,707,000	67,084,000
Commercial Banking | Equipment
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	6,547,000	6,547,000
Commercial Banking | Commercial real estate loans
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		71,297,000	62,239,000
Nonaccrual loans with an allowance	52,491,000	52,491,000	47,359,000
Nonaccrual loans with no allowance	21,498,000	21,498,000	23,938,000
Nonaccrual loans at ending balance	73,989,000	73,989,000	71,297,000
Loans 90 days past due and accruing	185,000	185,000	225,000
Amortized cost basis of collateral-dependent loans	69,173,000	69,173,000	66,934,000
Commercial Banking | Commercial real estate loans | Real estate
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	67,688,000	67,688,000	66,934,000
Commercial Banking | Commercial real estate loans | Equipment
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	1,485,000	1,485,000
Commercial Banking | Commercial real estate loans - owner occupied
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		676,000	624,000
Nonaccrual loans with an allowance	983,000	983,000	676,000
Nonaccrual loans with no allowance	0	0	0
Nonaccrual loans at ending balance	983,000	983,000	676,000
Loans 90 days past due and accruing	0	0	0
Commercial Banking | Commercial loans
Composition of impaired loans by portfolio segment and by class of financing receivable
Nonaccrual loans at beginning balance		4,147,000	2,627,000
Nonaccrual loans with an allowance	11,944,000	11,944,000	3,996,000
Nonaccrual loans with no allowance	176,000	176,000	151,000
Nonaccrual loans at ending balance	12,120,000	12,120,000	4,147,000
Loans 90 days past due and accruing	324,000	324,000	10,000
Amortized cost basis of collateral-dependent loans	8,081,000	8,081,000	150,000
Commercial Banking | Commercial loans | Real estate
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	3,019,000	3,019,000	$ 150,000
Commercial Banking | Commercial loans | Equipment
Composition of impaired loans by portfolio segment and by class of financing receivable
Amortized cost basis of collateral-dependent loans	$ 5,062,000	$ 5,062,000