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Stock-Based Compensation	3 Months Ended
Stock-Based Compensation	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation We issue stock-based incentive awards to our eligible employees under the 2019 Stock Incentive Plan ("2019 Plan") and to our eligible non-employee Directors under a Director Deferred Stock Ownership Plan. The 2019 Plan permits the granting of incentive stock options, nonqualified stock options, stock appreciation rights, performance stock, restricted stock and other stock-based awards. For the three months ended March 31, 2021 and 2020, total stock-based compensation expense primarily related to restricted stock and unit awards was $19 million and $11 million, respectively. Total unrecognized compensation expense related to unvested restricted stock and unit awards as of March 31, 2021 was $73 million, which is expected to be recognized over a weighted average period of 1.6 years.