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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Mandatory convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities (in shares)	0	39	0	0
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive securities (in shares)	9	7	9	7
Weighted average exercise price of options (in usd per share)	$ 26.80	$ 28.85	$ 26.80	$ 28.85