Shareholders' Equity - Additional Information (Details) - USD ($)	3 Months Ended					4 Months Ended	9 Months Ended		102 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Oct. 25, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Jun. 30, 2017	Nov. 30, 2014	Apr. 30, 2012
Equity, Class of Treasury Stock [Line Items]
Total cost of shares purchased	$ 500,000,000	$ 463,000,000	$ 350,000,000	$ 1,056,000,000	$ 101,000,000
Number of shares excluded from the calculation of diluted earnings per share (in shares)	0		0				0	0
2012 - Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization limit (up to)	$ 15,000,000,000.0						$ 15,000,000,000.0		$ 15,000,000,000.0	$ 5,000,000,000.0	$ 5,000,000,000.0	$ 5,000,000,000.0
Share repurchase, remaining authorized repurchase amount	$ 1,100,000,000						$ 1,100,000,000		$ 1,100,000,000
Shares purchased (in shares)	2,400,000		1,800,000			25,000	4,600,000	8,200,000	133,400,000
Total cost of shares purchased	$ 500,000,000		$ 350,000,000			$ 4,800,000	$ 961,000,000	$ 1,500,000,000	$ 13,900,000,000