Earnings Per Share - Schedule of Anti Dilutive Securities Excluded From Computation of Weighted Average Shares Outstanding (Details) - $ / shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities (in shares)	14	0	14	0
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities (in shares)	9	9	3	9
Weighted average exercise price of options (in usd per share)	$ 25.03	$ 26.80	$ 32.66	$ 26.80
Stock and performance awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities (in shares)	4	0	0	0