Stockholders' Equity (Narrative) (Details) - USD ($)		3 Months Ended	9 Months Ended
	Apr. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jan. 30, 2019
Class of Stock [Line Items]
Preferred stock, par value (USD per share)			$ 0.01		$ 0.01
Shares repurchased		$ 771,000,000		$ 1,991,000,000
Common Stock [Member]
Class of Stock [Line Items]
Share repurchase, authorized amount						$ 4,000,000,000.0
Shares repurchased (in shares)		20,000,000	0	49,000,000
Shares repurchased		$ 771,000,000		$ 2,000,000,000.0
Depositary Shares [Member]
Class of Stock [Line Items]
Number of shares issued (in shares)	2,500,000
Ownership interest in Class G shares	1.00%
Liquidation preference per share (USD per share)	$ 1,000
Series G Preferred Stock [Member]
Class of Stock [Line Items]
Fixed rate	5.375%		5.375%
Preferred stock, par value (USD per share)	$ 0.01
Liquidation preference per share (USD per share)	$ 100,000		$ 100,000
Proceeds from offering	$ 2,470,000,000