Earnings Per Share - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands			1 Months Ended	3 Months Ended
	Mar. 15, 2018	Feb. 12, 2018	Feb. 22, 2018	Mar. 31, 2018	Mar. 31, 2017	Jan. 19, 2018	Oct. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Accelerated share repurchase program (payment) receipt amount			$ 30,000,000			$ 150,000,000
Initial share value received						$ 120,000,000
Shares repurchased during the period (in shares)			2,700	15,000	6,000
Average purchase price (in dollars per share)			$ 55.02
Share repurchase program		$ 5,000,000,000					$ 1,500,000,000.0
Shares repurchased value				$ 836,000,000	$ 258,000,000
Increase in quarterly dividend (as a percent)		10.00%
Quarterly dividend per common share (in dollars per share)	$ 0.22	$ 0.20		$ 0.22	$ 0.18
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities				800	3,400