Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term	10 years
Stock-based compensation expense	$ 10,300	$ 13,306	$ 12,158
Tax benefit from stock-based compensation expense	2,198	2,805	2,613
Excess tax benefits	(579)	1,952	1,687
Unrecognized compensation costs	$ 13,894
Unrecognized compensation costs, period for recognition	1 year 11 months 12 days
Proceeds form exercise of stock options	$ 1,596	5,029	673
Intrinsic value of stock options exercised	$ 781	$ 5,324	$ 1,589
Weighted average grant date fair value (in dollars per share)	$ 14.69	$ 14.04	$ 12.80
Risk-free interest rate	1.45%	2.43%	2.60%
Expected volatility	26.00%	25.00%	24.10%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	5 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	97,842
Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Awards granted (in shares)	84,374
Performance period	3 years
Minimum range of target award of stock plan	0.00%
Maximum range of target award of stock plan	250.00%
Risk-free interest rate	1.42%
Expected volatility	26.70%

Maximum Range of Target Award for performance share awards under the long-term Relative Measure Program

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Minimum Range of Target Award for performance share awards under the long-term Relative Measure Program

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Share Based Compensation Arrangement By Share Based Payment Award Maximum Term

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Share-based Compensation Arrangement by Share-based Payment Award, Performance Period

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for 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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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of cash inflow from realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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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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