Aggregate number of common shares reserved for future issuance.

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Amount of cost capitalized for award under share-based payment arrangement.

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The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

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

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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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Price of a single share of a number of saleable stocks of a company.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Stock Based Awards and Other Equity Instruments - Additional Information (Details) - USD ($)		12 Months Ended
	Jun. 28, 2013	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 21, 2018	Dec. 20, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Capitalized stock based compensation as internal-use software and website development costs		$ 15,000,000	$ 19,000,000	$ 13,000,000
Common shares registered for issuance under incentive plan						17,500,000
Common stock share issuance under plan	15,000,000
Cash received from stock option exercises			2,000,000	6,000,000
2011 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares registered for issuance under incentive plan						17,400,000
Deferred Compensation Plan for Non Employee Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares registered for issuance under incentive plan						100,000
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock share issuance under plan					6,000,000
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for future stock-based awards under plan		8,400,000
2018 Plan \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing stock price		$ 28.78
Total intrinsic value			2,000,000	20,000,000
Total fair value of stock options vested		$ 14,000,000	15,000,000	38,000,000
Cash received from stock option exercises			$ 2,000,000	$ 6,000,000