Share Repurchase Programs and Dividends - Share Repurchase Programs (Details)	12 Months Ended			78 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) program shares
Equity, Class of Treasury Stock [Line Items]
Number of share repurchase programs authorized | program				7
Stock repurchase programs, authorized amount	$ 13,000,000,000.0			$ 13,000,000,000.0
Stock repurchased (in shares) | shares	6,378,025	34,090,566	16,606,157
Aggregate stock repurchase price	$ 145,000,000	$ 1,096,000,000	$ 799,000,000
Share Repurchase Program April 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchase programs, remaining authorized amount	$ 420,000,000			$ 420,000,000
Number of shares authorized to be repurchased (in shares) | shares	2,000,000,000.0			2,000,000,000.0
Stock repurchased (in shares) | shares	6,400,000	33,800,000	16,600,000
Aggregate stock repurchase price	$ 145,000,000	$ 1,100,000,000	$ 800,000,000
Average cost per share (in dollars per share) | $ / shares	$ 22.77	$ 32.09	$ 48.15