Shareholders' Equity - Additional Information (Details) - USD ($)	3 Months Ended				6 Months Ended		99 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2017	Nov. 30, 2014	Apr. 30, 2012
Equity, Class of Treasury Stock [Line Items]
Total cost of shares purchased		$ 463,000,000	$ 1,056,000,000	$ 101,000,000
Number of shares excluded from the calculation of diluted earnings per share (in shares)	100,000		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 authorization limit (in shares)	$ 1,600,000,000				$ 1,600,000,000		$ 1,600,000,000
Shares purchased (in shares)	0		5,800,000		2,200,000	6,400,000	130,900,000
Total cost of shares purchased	$ 0		$ 1,050,000,000		$ 461,000,000	$ 1,150,000,000	$ 13,400,000,000