Earnings Per Share - Narrative (Details) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jul. 15, 2019
Earnings Loss Per Share [Line Items]
Repurchases of common stock	$ 363,000,000	$ 34,000,000	$ 1,426,000,000	$ 1,010,000,000
Amount remaining under repurchase programs	$ 3,300,000,000		$ 3,300,000,000
Open Market Repurchase Program
Earnings Loss Per Share [Line Items]
Number of shares repurchased (in shares)	4.1		16.8
Repurchases of common stock	$ 400,000,000		$ 1,400,000,000
July 2019 Share Repurchase Program
Earnings Loss Per Share [Line Items]
Authorized amount under share repurchase program					$ 3,000,000,000.0