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
Cumulative effect adjustment for adoption of ASU 2016-13						(10)
Total other comprehensive income (loss)							(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
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)	$ (137)
Cumulative effect adjustment for adoption of ASU 2016-13	10
Total other comprehensive income (loss)	(139)
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
Beginning Balance at Mar. 31, 2020		$ 0	$ 16	(1,717)	17,589	(2,252)	168
Beginning Balance (Shares Issued) at Mar. 31, 2020		0	1,646,877,242
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(147)					(147)
Total other comprehensive income (loss)	(37)						(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
Total other comprehensive income (loss)							47
Preferred stock dividends						(14)
Stock-based compensation					19
Stock-based compensation (Shares)			3,949,308
Ending Balance at Mar. 31, 2021		$ 0	$ 17	(2,251)	19,750	(2,050)	254
Ending Balance (Shares Issued) at Mar. 31, 2021		10,062,500	1,683,861,226
Beginning Balance at Dec. 31, 2020	15,326	$ 0	$ 17	(2,251)	19,732	(2,378)	207
Beginning Balance (Shares Issued) at Dec. 31, 2020		10,062,500	1,679,911,918
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	527
Total other comprehensive income (loss)	30
Ending Balance at Jun. 30, 2021	15,942	$ 0	$ 17	(2,251)	19,817	(1,878)	237
Ending Balance (Shares Issued) at Jun. 30, 2021		10,062,500	1,685,006,608
Beginning Balance at Mar. 31, 2021		$ 0	$ 17	(2,251)	19,750	(2,050)	254
Beginning Balance (Shares Issued) at Mar. 31, 2021		10,062,500	1,683,861,226
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	186					186
Total other comprehensive income (loss)	(16)						(16)
Preferred stock dividends						(14)
Stock-based compensation					66
Stock-based compensation (Shares)			1,145,382
Ending Balance at Jun. 30, 2021	$ 15,942	$ 0	$ 17	$ (2,251)	$ 19,817	$ (1,878)	$ 237
Ending Balance (Shares Issued) at Jun. 30, 2021		10,062,500	1,685,006,608