Shareholders' Equity - Schedule of Shares Repurchase Plans (Details) - USD ($) $ / shares in Units, shares in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
2017 Program
Equity, Class of Treasury Stock [Line Items]
Amount of common stock authorized for repurchase		$ 1,400,000,000.0
Shares Purchased	3.3
Average Cost per Share (USD per share)	$ 105.31
Total Purchased	$ 350,000,000
2018 Program
Equity, Class of Treasury Stock [Line Items]
Amount of common stock authorized for repurchase	$ 1,200,000,000.0