Equity - Stock Options (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) company $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term	10 years
Incremental vesting | company	0.33
Vesting period	3 years
Exercise price for awards granted as percentage of market value on the date of grant	100.00%
Weighted-average grant-date fair value of the stock options granted (in dollars per share)	$ 12.54	$ 21.63	$ 9.80
Options
Outstanding at the beginning of the period (in shares) | shares	6,143
Granted (in shares) | shares	1,002
Exercised (in shares) | shares	(375)
Lapsed (in shares) | shares	(9)
Outstanding at the end of the period (in shares) | shares	6,761	6,143
Exercisable at the end of the period (in shares) | shares	4,924
Weighted- average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 55.05
Granted (in dollars per share)	79.02
Exercised (in dollars per share)	23.72
Lapsed (in dollars per share)	20.09
Outstanding at the end of the period (in dollars per share)	60.39	$ 55.05
Exercisable at the end of the period (in dollars per share)	$ 51.90
Weighted- average remaining life (in years)
Outstanding	5 years 10 months 24 days	6 years 2 months 12 days
Exercisable	4 years 10 months 24 days
Aggregate intrinsic value
Outstanding | $	$ 207	$ 242
Exercisable | $	186
Aggregate intrinsic value of options exercised | $	22	$ 215	$ 371
Total fair value of options vested | $	13
Unrecognized compensation cost | $	$ 6
Period for recognition of unrecognized compensation cost	2 years