Stock-Based Compensation - Changes in Outstanding Stock Options (Details) - Time Based [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	230	317	474
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(42)	(83)	(152)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	0	0	(2)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	(3)	(4)	(3)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	185	230	317
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Beginning Balance	$ 20.73	$ 18.97	$ 17.47
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	17.73	14.41	14.32
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price	0	0	26.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	9.91	11.97	11.09
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance	$ 21.56	$ 20.73	$ 18.97
Options Vested During the Year	$ 0	$ 2	$ 9

Options Vested During the Year.

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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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- Definition

Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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Weighted average price of options that were either forfeited or expired.

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- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Number of options outstanding, including both vested and non-vested options.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Number of share options (or share units) exercised during the current period.

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