Stockholders' Equity (Narrative) (Details) - USD ($)				9 Months Ended
	Jun. 01, 2021	Mar. 30, 2021	Mar. 18, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jan. 30, 2019
Class of Stock [Line Items]
Preferred stock, aggregate liquidation preference				$ 10,100,000,000		$ 7,850,000,000
Preferred stock, par value (USD per share)				$ 0.01		$ 0.01
Depositary Shares [Member]
Class of Stock [Line Items]
Shares redeemed (in shares)	24,000,000
Liquidation preference per share (USD per share)	$ 25	$ 25	$ 1,000
Preferred stock, aggregate liquidation preference	$ 600,000,000
Ownership interest in shares	2.50%	2.50%	1.00%
Series J Preferred Stock [Member]
Class of Stock [Line Items]
Fixed rate		4.45%		4.45%
Liquidation preference per share (USD per share)		$ 1,000		$ 1,000
Preferred stock, par value (USD per share)		$ 0.01
Proceeds from offering		$ 584,000,000
Series I Preferred Stock [Member]
Class of Stock [Line Items]
Fixed rate			4.00%	4.00%
Liquidation preference per share (USD per share)			$ 100,000	$ 100,000
Preferred stock, par value (USD per share)			$ 0.01
Proceeds from offering			$ 2,200,000,000
Common Stock [Member]
Class of Stock [Line Items]
Share repurchase, authorized amount							$ 4,000,000,000
Shares repurchased (in shares)				0	0
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Shares redeemed (in shares)	600,000
Fixed rate	6.00%			0.00%
Liquidation preference per share (USD per share)				$ 1,000