Share Repurchase Programs and Dividends - Share Repurchase Programs (Details)	12 Months Ended			42 Months Ended	54 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) program	Apr. 30, 2018 USD ($)
Equity, Class of Treasury Stock [Line Items]
Stock repurchase programs, authorized amount	$ 13,000,000,000				$ 13,000,000,000
Number of share repurchase programs authorized | program					7
Stock repurchased (in shares) | shares	16,606,157	33,900,000	119,823,621	278,900,000
Aggregate stock repurchase price	$ 799,000,000	$ 1,563,000,000	$ 4,416,000,000	$ 11,300,000,000
Average cost per share (in dollars per share) | $ / shares		$ 45.68	$ 36.86	$ 40.69
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	$ 1,700,000,000				$ 1,700,000,000
Stock repurchased (in shares) | shares	16,600,000
Aggregate stock repurchase price	$ 800,000,000
Average cost per share (in dollars per share) | $ / shares	$ 48.15