Equity (Repurchase Programs) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Feb. 29, 2020	Dec. 31, 2019	Apr. 30, 2019
Class of Stock [Line Items]
Treasury stock (in shares)	209,000,000		209,000,000		190,000,000
Treasury stock, value	$ 7,897,000,000		$ 7,897,000,000		$ 7,374,000,000
Series A Common Stock | Common Stock
Class of Stock [Line Items]
Treasury stock (in shares)	3,000,000		3,000,000
Treasury stock, value	$ 171,000,000		$ 171,000,000
Series C Common Stock | Common Stock
Class of Stock [Line Items]
Shares repurchased (in shares)	0	0	19,400,000
Treasury stock (in shares)	206,000,000		206,000,000
Treasury stock, value	$ 7,700,000,000		$ 7,700,000,000
February 2020 Repurchase Program | Common Stock
Class of Stock [Line Items]
Stock repurchase program, authorized amount				$ 2,000,000,000
February 2020 Repurchase Program | Series C Common Stock | Common Stock
Class of Stock [Line Items]
Shares repurchased, value			$ 523,000,000
Shares repurchased, average price per share (in dollars per share)			$ 26.87
April 2019 Repurchase Program | Common Stock
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 1,000,000,000