Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Preferred Stock [Member]	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ 0
Adjusted balance, beginning of period					11,055
Beginning balance at Dec. 31, 2018				$ 4,378	11,055	$ (1,091)	$ (1,579)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive and stock compensation plans				(68)
Stock-based compensation plans expense				55
Issuance of shares for warrant exercise				(36)
Net income	$ 630				630
Dividends declared on preferred stock	(5)				(5)
Dividends declared on common stock					(108)
Treasury stock acquired						0
Issuance of shares under incentive and stock compensation plans						71
Net shares acquired related to employee incentive and stock compensation plans						(30)
Issuance of shares for warrant exercise						36
Total other comprehensive loss							694
Ending balance at Mar. 31, 2019	$ 14,340	$ 334	$ 4	4,329	11,572	(1,014)	(885)
Preferred Shares Outstanding, beginning of period at Dec. 31, 2018		13,800
Preferred Shares Outstanding
Issuance of preferred shares		0
Preferred Shares Outstanding, end of period at Mar. 31, 2019		13,800
Common Shares Outstanding, beginning of period (in thousands) at Dec. 31, 2018			359,151
Shares Granted or Issued, Share-based Payment Arrangement [Abstract]
Treasury stock acquired			0
Issuance of shares under incentive and stock compensation plans			1,534
Return of shares under incentive and stock compensation plans to treasury stock			(601)
Issuance of shares for warrant exercise			781
Common Shares Outstanding, at end of period at Mar. 31, 2019			360,865
Shares Granted or Issued, Share-based Payment Arrangement [Abstract]
Cash dividends declared per common share	$ 0.30
Cash dividends declared per preferred share	$ 375.00
Beginning balance at Dec. 31, 2019	$ 16,270			4,312	12,685	(1,117)	52
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive and stock compensation plans				(79)
Stock-based compensation plans expense				53
Issuance of shares for warrant exercise				0
Net income	273				273
Dividends declared on preferred stock	(5)				(5)
Dividends declared on common stock					(116)
Treasury stock acquired						(150)
Issuance of shares under incentive and stock compensation plans						82
Net shares acquired related to employee incentive and stock compensation plans						(35)
Issuance of shares for warrant exercise						0
Total other comprehensive loss							(1,009)
Ending balance at Mar. 31, 2020	$ 15,266	$ 334	$ 4	$ 4,286	$ 12,819	$ (1,220)	$ (957)
Preferred Shares Outstanding, beginning of period at Dec. 31, 2019		13,800
Preferred Shares Outstanding
Issuance of preferred shares		0
Preferred Shares Outstanding, end of period at Mar. 31, 2020		13,800
Common Shares Outstanding, beginning of period (in thousands) at Dec. 31, 2019			359,570
Shares Granted or Issued, Share-based Payment Arrangement [Abstract]
Treasury stock acquired	(2,700)		(2,661)
Issuance of shares under incentive and stock compensation plans			1,685
Return of shares under incentive and stock compensation plans to treasury stock			(660)
Issuance of shares for warrant exercise			0
Common Shares Outstanding, at end of period at Mar. 31, 2020			357,934
Shares Granted or Issued, Share-based Payment Arrangement [Abstract]
Cash dividends declared per common share	$ 0.325
Cash dividends declared per preferred share	$ 375.00