Shareholders' Equity - Schedule of Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2019
2018 Program
Equity, Class of Treasury Stock [Line Items]
Shares Acquired (in shares)	0.0			8.8
Average Cost per Share (USD per share)	$ 0			$ 67.97
Total Acquired	$ 0	$ 300	$ 300	$ 600
2019 Program
Equity, Class of Treasury Stock [Line Items]
Shares Acquired (in shares)	9.4			9.4
Average Cost per Share (USD per share)	$ 53.15			$ 53.15
Total Acquired	$ 500			$ 500