Employee Benefit Plans - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2018	Dec. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Years of employment benefits are based upon			5 years
Bank-owned life insurance ("BOLI")			$ 264,854,000	$ 247,474,000
Bank-owned life insurance income		$ 6,600,000	7,393,000	5,994,000	$ 6,620,000
Defined contribution plan, cost			2,400,000
Defined contribution plan, employer discretionary contribution amount			204,000	213,000
Employee stock ownership plan, compensation expense			4,850,000	4,052,000	3,161,000
RIM Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			(12,610,000)	(15,650,000)
Defined contribution plan, cost			73,000	12,000	4,000
Employee stock ownership plan, compensation expense			455,000	348,000	215,000
Defined benefit plan, net periodic benefit cost (credit)			1,205,000	1,405,000	1,069,000
RIM Plan | Acquired Roselle Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, net periodic benefit cost (credit)			12,000	9,000	11,000
RIM Plan | Acquired Freehold Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, net periodic benefit cost (credit)			8,000	1,000
RIM Plan | Acquired RSI Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, net periodic benefit cost (credit)			38,000
Post-retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			(19,783,000)	(26,335,000)
Defined benefit plan, net periodic benefit cost (credit)			1,257,000	1,695,000	1,386,000
Post-retirement Plan | Acquired RSI Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			(2,047,000)
Defined benefit plan, net periodic benefit cost (credit)			(244,000)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			181,620,000	181,716,000
Defined contribution plan, cost				2,100,000	1,700,000
Defined benefit plan, net periodic benefit cost (credit)			(11,966,000)	(9,471,000)	(2,880,000)
Pension Plan | Acquired RSI Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded (unfunded) status of plan			1,004,000
Defined benefit plan, net periodic benefit cost (credit)			(107,000)
Other Pension, Postretirement and Supplemental Plans | Acquired Freehold Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, net periodic benefit cost (credit)			9,000	1,000
Defined benefit plan, annual benefit payment amount			$ 12,000
Defined benefit plan, benefit payment installment period			120 months
Liability, defined benefit plan			$ 390,000	459,000
Other Pension, Postretirement and Supplemental Plans | Acquired RSI Plan
Defined Benefit Plan Disclosure [Line Items]
Liability, defined benefit plan			257,000
Defined benefit plan, expense			$ 7,000
Postemployment Retirement Benefits | Acquired Freehold Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, benefit payment installment period			120 months
Defined benefit plan, percent return on deferrals			10.00%
Liability, defined benefit plan			$ 399,000	765,000
Defined benefit plan, expense			0	0
Postemployment Retirement Benefits | Acquired RSI Plan
Defined Benefit Plan Disclosure [Line Items]
Liability, defined benefit plan			351,000
Defined benefit plan, expense			$ 8,000
Defined benefit plan, period directors elected not to receive director fees			5 years
Defined benefit plan, benefit payable accrual period			10 years
Defined benefit plan, payment commencement age			65 years
Defined benefit plan, payment commencement period from plan implementation			5 years
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			4.50%
Maximum | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			4.50%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			3.00%
Minimum | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			3.00%
Columbia Bank Employee Stock Ownership Plan
Defined Benefit Plan Disclosure [Line Items]
Proceeds from repayments of loans by employee stock ownership plans	$ 45,400,000
Loan term	20 years		20 years
Shares contributed to ESOP (in shares)	4,542,855
Fixed interest rate	4.75%
Employee stock ownership plan, compensation expense			$ 4,900,000	$ 4,100,000	$ 3,200,000