Stock Based Awards and Other Equity Instruments - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Capitalized stock based compensation as internal-use software and website development costs	$ 3	$ 3
Cash received from stock option exercises		3
Income tax benefits from exercise or settlement of stock-based awards	$ 3	14
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock options issued	611,000
RSU
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSU's issued under incentive plan	2,590,000
2011 Plan \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock options issued	611,235
Term of stock options, granted	10 years
Stock awards vest period	4 years
Closing stock price	$ 40.89
Total intrinsic value	$ 3	$ 7
Weighted-average grant date fair value of options granted	$ 17.60	$ 17.20
Total fair value of stock options vested	$ 8	$ 13
Cash received from stock option exercises		$ 3
2011 Plan \| RSU
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock awards vest period	4 years
RSU's issued under incentive plan	2,590,380

Income tax benefits associated with exercise settlement of stock based awards.

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- Definition

Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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- Definition

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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No definition available.

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- Definition

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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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