Employee Benefit Plans - Additional Information (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total fair value of shares vested	$ 874,000	$ 951,000
Intrinsic value of options exercised	365,000	250,000
Aggregate intrinsic value of total options outstanding	1,860,000
Aggregate intrinsic value of exercisable options	1,460,000
Cash received from options exercised	317,000
Tax benefits from exercise of stock options	$ 0	$ 0
Total unvested stock options	174,900	125,800
Shares, Granted	85,500	20,500
Unvested stock options vested	36,400
Weighted average calculated value of stock options granted	$ 3.85	$ 2.22
Estimated dividend yield term	The dividend yield is the estimated dividend we expect to pay over the next four or five years.
Defined contribution plan, number of common stock outstanding, shares	5,687,914	5,098,068
Employee Stock Ownership Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Defined contribution plan, description	The Company makes contributions up to 3% of each participant’s annual compensation and the Company matches 50% of the next 2% contributed by the employee
Maximum annual contributions amount per employee	$ 18,500	$ 18,000
Maximum annual contributions percentage per employee	3.00%
Employer matching percentage of compensation contributed	50.00%
Employer matching percentage of employees compensation contributed	2.00%
Contributions by company	$ 341,000	306,000
Common stock related to 401(k) Employee Stock Ownership Plan	1,370,000	950,000
Fair Value of Common stock related to 401(k) Employee Stock Ownership Plan	$ 1,650,000	1,320,000
Employee Stock Ownership Plan \| Defined Benefit Plans Adjustment
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of periods available to purchase shares following distribution	2
Fair Value of Common stock related to 401(k) Employee Stock Ownership Plan	$ 0	0
Performance Share Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense recognized	68,000	$ 56,000
Unrecorded compensation expense	$ 412,000
Weighted average period of unrecorded compensation costs	1 year 9 months 18 days
Stock Compensation Plan \| Employee Stock Ownership Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Defined contribution plan, number of common stock outstanding, shares	68,889,000	53,715,000
Defined contribution plan, number of common stock outstanding, shares unallocated	0	0
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend payment period	5 years
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend payment period	4 years
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for possible issuance	300,000
Equity incentive plan, expiration period	10 years
2015 Equity Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity incentive plan, expiration period	10 years

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Share based compensation arrangement by share based payment award estimated dividend yield term.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Amount of discretionary contributions made by an employer to a defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Description of defined contribution pension and other postretirement plans. Includes, but is not limited to, plan utilized, employee group covered, and employer matching contributions.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Fair value of unearned shares held by the employee stock ownership plan (ESOP).

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of suspense shares held by the Employee Stock Option Plan at balance sheet date. Suspense shares are shares that have not been released, committed to be released or allocated to individual participant accounts.

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Carrying amount of the par value of temporary equity outstanding. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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