Shareholders' Equity - Additional Information (Details) - USD ($)	3 Months Ended		102 Months Ended	108 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020	Mar. 31, 2021	Nov. 30, 2020	Jun. 30, 2017	Nov. 30, 2014	Apr. 30, 2012
Equity, Class of Treasury Stock [Line Items]
Total cost of shares purchased	$ 50,000,000	$ 463,000,000
Number of shares excluded from the calculation of diluted earnings per share (in shares)	100,000	0
2012 - Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization limit (up to)	$ 20,000,000,000.0			$ 20,000,000,000.0	$ 5,000,000,000.0	$ 5,000,000,000.0	$ 5,000,000,000.0	$ 5,000,000,000.0
Share repurchase, remaining authorized repurchase amount	$ 5,200,000,000			$ 5,200,000,000
Shares purchased (in shares)	200,000	2,200,000		137,500,000
Total cost of shares purchased	$ 50,000,000	$ 461,000,000	$ 14,800,000,000