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	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 50	$ 69	$ 110	$ 105
Denominator:
Weighted average shares used to compute Basic EPS	139,324	137,574	138,937	138,239
Weighted average effect of dilutive securities:
Stock options	29	518	207	305
RSUs/MSUs	1,028	2,421	1,674	1,607
Weighted average shares used to compute Diluted EPS	140,381	140,513	140,818	140,151
Basic EPS	$ 0.36	$ 0.50	$ 0.79	$ 0.76
Diluted EPS	$ 0.36	$ 0.49	$ 0.78	$ 0.75

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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