Borrowings - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Ratio of line of credit to eligible assets	45.00%
Line of credit	$ 271,800,000
Ratio of line of credit to total assets	10.00%
Ratio of eligible assets to borrowing capacity	45.00%
Additional borrowing capacity	$ 1,220,000,000
Long-term FHLB advances	$ 14,500,000	$ 14,800,000
Amortization period of FHLB advance	30 years
Loans pledged as collateral	$ 0	0
FHLB discount window advances outstanding	0	0
Interest paid (less than)	$ 3,813,000	6,009,000	$ 5,640,000
Alaska limit on borrowing, percent of total assets	35.00%
Alaska limit on borrowing, total assets	$ 948,000,000	736,000,000
Securities sold under repurchase agreements	0	0
Interest expense on deposits, borrowings and junior subordinated debentures	$ 3,779,000	$ 6,051,000	$ 5,641,000
Weighted average interest rate	2.90%	3.12%	3.39%
Minimum
Debt Instrument [Line Items]
Term of FHLB advances	18 years
Fixed rate of FHLB advance	1.23%
Maximum
Debt Instrument [Line Items]
Term of FHLB advances	20 years
Fixed rate of FHLB advance	3.25%
Note Agreement With Federal Reserve Bank
Debt Instrument [Line Items]
Loans pledged as collateral	$ 50,700,000
Interest paid (less than)	1,000	$ 1,000
Discount Window
Debt Instrument [Line Items]
Loans pledged as collateral	32,200,000
FHLB and Secured Debt
Debt Instrument [Line Items]
Interest expense on deposits, borrowings and junior subordinated debentures	$ 320,000	$ 387,000	$ 291,000