Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
NUMERATOR:
Net income (loss)	$ 348	$ (915)	$ 463	$ (1,009)
DENOMINATOR:
WEIGHTED AVERAGE SHARES OUTSTANDING, Basic (in shares)	591	563	591	539
Dilutive effects of convertible notes	22	0	19	0
Dilutive effect of stock warrants	1	0	1	0
Dilutive effect of restricted stock units	1	0	1	0
Diluted	615	563	612	539
NET INCOME (LOSS) PER SHARE:
BASIC (in USD per share)	$ 0.59	$ (1.63)	$ 0.78	$ (1.87)
DILUTED (in USD per share)	0.57	$ (1.63)	0.76	$ (1.87)
Initial conversion price (in USD per share)	$ 38.48		$ 38.48