Share Repurchase Programs and Dividends - Share Repurchase Programs (Details)	3 Months Ended			6 Months Ended	60 Months Ended
	Mar. 31, 2019 USD ($) shares	Jun. 30, 2018 USD ($) shares	Mar. 31, 2018 USD ($) shares	Jun. 30, 2019 USD ($) $ / shares shares	Jun. 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
Number of share repurchase programs authorized | program					7
Stock repurchased (in shares) | shares	16,947,393	8,175,007	8,431,150		295,600,000
Aggregate stock repurchase price	$ 610,000,000	$ 350,000,000	$ 449,000,000		$ 11,900,000,000
Average cost per share (in dollars per share) | $ / shares					$ 40.43
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				$ 1,100,000,000	$ 1,100,000,000
Stock repurchased (in shares) | shares				16,700,000
Aggregate stock repurchase price				$ 600,000,000
Average cost per share (in dollars per share) | $ / shares				$ 36.02