Consolidated Statements Of Changes In Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Capital Surplus	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
Cumulative effect of change in accounting principle				$ 0
BALANCE (in shares) at Dec. 31, 2018		160.1
BALANCE at Dec. 31, 2018	$ 7,507	$ 1,141	$ 2,148	(609)	$ 8,781	$ (3,954)
Net (loss) income	339				339
Other comprehensive income (loss), net of tax	96			96
Cash dividends declared on common stock	(105)				(105)
Purchase of common stock	(434)		0			(434)
Purchase of common stock (in shares)		(5.2)
Net issuance of common stock under employee stock plans	(4)		(13)		(22)	31
Net issuance of common stock under employee stock plans (in shares)		0.5
Share-based compensation	24		24
BALANCE at Mar. 31, 2019	7,409	$ 1,141	2,159	(513)	8,979	(4,357)
BALANCE (in shares) at Mar. 31, 2019		155.4
BALANCE (in shares) at Dec. 31, 2019		142.1
BALANCE at Dec. 31, 2019	7,327	$ 1,141	2,174	(235)	9,538	(5,291)
Net (loss) income	(65)				(65)
Other comprehensive income (loss), net of tax	409			409
Cash dividends declared on common stock	(94)				(94)
Purchase of common stock	(195)		0			(195)
Purchase of common stock (in shares)		(3.4)
Net issuance of common stock under employee stock plans	(1)		(14)		(3)	16
Net issuance of common stock under employee stock plans (in shares)		0.3
Share-based compensation	8		8
BALANCE at Mar. 31, 2020	$ 7,402	$ 1,141	$ 2,168	$ 174	$ 9,389	$ (5,470)
BALANCE (in shares) at Mar. 31, 2020		139.0