Earnings (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share Table [Line Items]
Net income (loss) available to common stockholders	$ (518)	$ 194
Basic weighted-average shares	1,213,019	1,211,489
Effect of dilutive securities:
Diluted weighted-average shares (1)	1,213,019	1,213,592
Earnings (loss) per common share:
Basic	$ (0.43)	$ 0.16
Diluted	$ (0.43)	$ 0.16
Nonvested restricted stock units [Member]
Effect of dilutive securities:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	1,845
Stock Options [Member]
Effect of dilutive securities:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	258
Nonvested restricted stock units [Member]
Earnings Loss Per Common Share from Continuing Operations Textuals [Abstract]
Number of weighted-average shares excluded from computation of diluted earnings per common share	1,300

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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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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