Stock-Based Compensation - Stock Option Activity (Details) - $ / shares shares in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Options
Outstanding at beginning of period (in shares)	67	114	232
Exercised (in shares)	(37)	(42)	(114)
Forfeited/Expired (in shares)	(2)	(5)	(4)
Outstanding at end of period (in shares)	28	67	114
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in usd per share)	$ 23.13	$ 24.00	$ 26.36
Exercised (in usd per share)	21.28	25.59	26.40
Forfeited/Expired (in usd per share)	22.76	25.32	74.88
Outstanding at end of period (in usd per share)	$ 25.55	$ 23.13	$ 24.00

For presentations that combine terminations, 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 or that expired.

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

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

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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

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

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