Share Repurchase Programs and Dividends - Share Repurchase Programs (Details)	3 Months Ended				9 Months Ended	63 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) shares	Jun. 30, 2018 USD ($) shares	Mar. 31, 2018 USD ($) shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) program $ / shares shares	Apr. 30, 2018 USD ($)
Equity, Class of Treasury Stock [Line Items]
Stock repurchase programs, authorized amount	$ 13,000,000,000.0				$ 13,000,000,000.0	$ 13,000,000,000.0
Number of share repurchase programs authorized | program						7
Stock repurchased (in shares) | shares	7,275,610	16,947,393	8,175,007	8,431,150		302,900,000
Aggregate stock repurchase price	$ 201,000,000	$ 610,000,000	$ 350,000,000	$ 449,000,000		$ 12,100,000,000
Average cost per share (in dollars per share) | $ / shares						$ 40.12
Share Repurchase Program April 2018 [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase programs, authorized amount							$ 2,000,000,000.0
Stock repurchase programs, remaining authorized amount	$ 850,000,000				$ 850,000,000	$ 850,000,000
Stock repurchased (in shares) | shares	7,300,000				23,900,000
Aggregate stock repurchase price	$ 200,000,000				$ 800,000,000
Average cost per share (in dollars per share) | $ / shares	$ 27.49				$ 33.43