Earnings Per Share - Reconciliation of Weighted Average Number of Shares of Common Stock Outstanding In Calculating EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income	$ 34	$ 32	$ 60	$ 36
Denominator:
Weighted average shares used to compute Basic EPS	139,070	137,831	138,744	138,572
Weighted average effect of dilutive securities:
Stock options	187	278	296	198
RSUs/MSUs	1,548	1,510	1,997	1,201
Weighted average shares used to compute Diluted EPS	140,805	139,619	141,037	139,971
Basic EPS	$ 0.24	$ 0.23	$ 0.43	$ 0.26
Diluted EPS	$ 0.24	$ 0.23	$ 0.43	$ 0.26

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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