Earnings (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share Table [Line Items]
Net income (loss) available to common stockholders	$ 194	$ 152
Basic weighted-average shares	1,211,489	827,509
Effect of dilutive securities:
Diluted weighted-average shares	1,213,592	830,197
Earnings (loss) per common share:
Basic	$ 0.16	$ 0.18
Diluted	$ 0.16	$ 0.18
Nonvested restricted stock units [Member]
Effect of dilutive securities:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,845	2,095
Stock Options [Member]
Effect of dilutive securities:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	258	593