Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Preferred Stock	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2019		$ 0	$ 16	$ (1,717)	$ 17,561	$ (2,253)	$ 270
Beginning Balance (Shares Issued) at Dec. 31, 2019		0	1,642,488,911
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 11					11
Cumulative effect adjustment for adoption of ASU 2016-13	10					(10)
Total other comprehensive income (loss)	(101)						(101)
Stock-based compensation					28
Stock-based compensation (Shares)			4,388,331
Ending Balance at Mar. 31, 2020		$ 0	$ 16	(1,717)	17,589	(2,252)	168
Ending Balance (Shares Issued) at Mar. 31, 2020		0	1,646,877,242
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)						(147)
Total other comprehensive income (loss)							(37)
Stock issuance (Par value)		$ 0	$ 0
Preferred stock issuance (Value in excess of par)					975
Common stock issuance (Value in excess of par)					975
Stock issuance (Shares)		10,062,500	29,382,500
Preferred stock dividends						(5)
Stock-based compensation					50
Stock-based compensation (Shares)			493,824
Ending Balance at Jun. 30, 2020		$ 0	$ 17	(1,717)	19,590	(2,405)	131
Ending Balance (Shares Issued) at Jun. 30, 2020		10,062,500	1,676,753,566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)						(155)
Total other comprehensive income (loss)							20
Preferred stock dividends						(14)
Stock-based compensation					97
Stock-based compensation (Shares)			2,674,643
Ending Balance at Sep. 30, 2020		$ 0	$ 17	(1,717)	19,687	(2,574)	151
Ending Balance (Shares Issued) at Sep. 30, 2020		10,062,500	1,679,428,209
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)						210
Total other comprehensive income (loss)							56
Preferred stock dividends						(14)
Repurchase of common stock				(535)
Stock-based compensation					45
Stock-based compensation (Shares)			483,709
Ending Balance at Dec. 31, 2020	15,326	$ 0	$ 17	(2,251)	19,732	(2,378)	207
Ending Balance (Shares Issued) at Dec. 31, 2020		10,062,500	1,679,911,918
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	341					341
Total other comprehensive income (loss)	47						47
Preferred stock dividends						(14)
Stock-based compensation					19
Stock-based compensation (Shares)			3,949,308
Ending Balance at Mar. 31, 2021	$ 15,719	$ 0	$ 17	$ (2,251)	$ 19,750	$ (2,050)	$ 254
Ending Balance (Shares Issued) at Mar. 31, 2021		10,062,500	1,683,861,226