Cash and Cash Equivalents - Additional Information (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 61,335,000	$ 18,473,000
Federal Reserve Bank of Boston
Cash And Cash Equivalents [Line Items]
Reserve balance of cash and due from banks	31,500,000	12,700,000
New Hampshire
Cash And Cash Equivalents [Line Items]
Pledged amount to federal banking department	$ 500,000	$ 500,000