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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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Number of shares authorized for issuance under share-based payment arrangement.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

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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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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Number of shares issued in lieu of cash for services contributed to the entity. Number of shares includes, but is not limited to, shares issued for services contributed by vendors and founders.

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Share-Based Compensation (Narrative) (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	May 22, 2019	Feb. 26, 2019	Dec. 31, 2020 USD ($) Director $ / shares shares	Dec. 31, 2019 Director $ / shares shares	Dec. 31, 2018 USD ($) Director $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period			10 years
Stock options awarded			0	0	0
Unrecognized compensation expense \| $			$ 0
Aggregate intrinsic value \| $					$ 236
Proceeds from stock options exercised \| $					$ 320
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value \| $ / shares			$ 19.54	$ 29.78	$ 29.03
Shares issued in lieu of cash			8,439	4,192	6,363
Number of non-employee directors \| Director			4	3	5
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense \| $			$ 2,000
Expected recognition expense period, weighted average period in years			1 year 9 months 18 days
TSR Performance Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	2 years 7 months 9 days	2 years 10 months 2 days			2 years 10 months 2 days
Risk free interest rate	2.18%	2.43%			2.39%
Expected dividend yield	3.60%	3.20%			2.83%
Expected stock price volatility	22.00%	21.30%			21.20%
2015 Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant			156,000
Non-employee Directors Stock Incentive Plan [Member] \| Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required service period			1 year	1 year	1 year
Restricted shares of common stock awarded			12,798	8,226	7,370
Grant date fair value \| $ / shares			$ 17.57	$ 27.33	$ 33.90
Non-employee Directors Stock Incentive Plan [Member] \| Restricted Stock Awards [Member] \| Vested Immediately [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting percentage			50.00%
Restricted shares of common stock awarded			6,399	4,113	3,690
Non-employee Directors Stock Incentive Plan [Member] \| Restricted Stock Awards [Member] \| Vested After Completion of One-Year Service Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting percentage			50.00%
Restricted shares of common stock awarded			6,399	4,113	3,680
Management Stock Incentive Plan [Member] \| Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required service period			3 years	3 years	3 years
Grant date fair value \| $ / shares			$ 25.02	$ 25.60	$ 27.76
Share-based vesting date				Feb. 26, 2022	Feb. 27, 2021
Management Stock Incentive Plan [Member] \| Restricted Stock Awards [Member] \| TSR Performance Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Required service period				3 years	1 year
Management Stock Incentive Plan [Member] \| PSUs [Member] \| ROAE Return on Average Equity [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting percentage			50.00%
Required service period			3 years
Share-based vesting description			The shares earned based on the achievement of the ROAE performance requirement, if any, will vest on the third anniversary of the grant date assuming the recipient’s continuous service to the Company.
Management Stock Incentive Plan [Member] \| PSUs [Member] \| ROAA Performance Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting percentage			50.00%	50.00%
Required service period			3 years
Share-based vesting description			The shares earned based on the achievement of the ROAA performance requirement, if any, will vest on the third anniversary of the grant date assuming the recipient’s continuous service to the Company. If earned at target level, members of management will receive up to 23,302 shares of our common stock in the aggregate.
Management Stock Incentive Plan [Member] \| PSUs [Member] \| TSR Performance Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, vesting percentage				50.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			5 years
Maximum [Member] \| Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Maximum [Member] \| 2015 Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of grants authorized			438,076
Maximum [Member] \| Management Stock Incentive Plan [Member] \| Restricted Stock Awards [Member] \| ROAA Performance Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares of common stock awarded			23,302
Maximum [Member] \| Management Stock Incentive Plan [Member] \| Restricted Stock Awards [Member] \| Vested After Completion of Three-Year Service Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares of common stock awarded			58,806	54,476	37,676
Maximum [Member] \| Management Stock Incentive Plan [Member] \| Restricted Stock Awards [Member] \| TSR Performance Requirement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares of common stock awarded				21,970	14,877
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Minimum [Member] \| Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			2 years