Stockholders' Equity - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Shares
Beginning balance, outstanding (in shares)	405,000
Exercised (in shares)	(10,000)	0	0
Ending balance, outstanding (in shares)	395,000	405,000
Weighted Average Exercise Price
Beginning balance, outstanding (usd per share)	$ 64.79
Exercised (usd per share)	33.02
Ending balance, outstanding (usd per share)	$ 65.59	$ 64.79
Outstanding, Aggregate Intrinsic Value	$ 100	$ 100
Outstanding, Weighted Average Remaining Contractual term	5 years 6 months	5 years 6 months

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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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 remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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

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