Share-Based Payments - Employee Stock Purchase Plan (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Issued During Period, Shares, Employee Stock Purchase Plans	47,000	20,000
Proceeds from common stock issued pursuant to ESPP	$ 1,457,000	$ 597,000	$ 0
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum	0.10%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	206,600
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	2,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	15.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans	47,022	20,178
Proceeds from common stock issued pursuant to ESPP	$ 1,500,000	$ 597,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,000,000.0
Measurement Input, Price Volatility [Member] \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum	18.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum		21.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum	2.20%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate		2.00%
Measurement Input, Expected Dividend Rate [Member] \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		2.50%
Measurement Input, Expected Term [Member] \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	6 years	6 years
Minimum [Member] \| Measurement Input, Expected Dividend Rate [Member] \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	2.60%
Maximum \| Measurement Input, Expected Dividend Rate [Member] \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	3.50%

The cash inflow associated with the amount received from the stock plan during the period.

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Discount rate from fair value on purchase date that participants pay for shares.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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