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Accumulated Other Comprehensive Loss and Shareholders' Equity - Changes in Shareholders' Equity (Deficit) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended					6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period	$ 1,240	$ 1,603	$ 2,225	$ 3,588	$ 3,731	$ 2,225	$ 3,731
Balance at beginning of period (as adjusted)		1,240				1,240			$ 2,225
Net income		232	375	667	420	607	1,087
Other comprehensive income		34	31	(385)	162	65	(223)
Dividends		(159)	(139)	(145)	(118)
Share-based compensation plans		30	(62)	45	(48)
Purchase of treasury stock		(500)	(828)	(850)	(782)
Balance at end of period		$ 1,240	$ 1,603	$ 2,920	$ 3,588	1,240	2,920
Cash dividends (in USD per share)		$ 0.41	$ 0.33	$ 0.48	$ 0.41
Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period	$ 5	$ 5	$ 5	$ 5	$ 5	$ 5	$ 5
Balance at beginning of period (in shares)	330.6	334.1	339.1	354.8	359.1	339.1	359.1
Share-based compensation plans (in shares)		0.2	1.7	0.1	1.3
Purchase of treasury stock (in shares)		(3.7)	(6.7)	(6.2)	(5.6)
Balance at end of period		$ 5	$ 5	$ 5	$ 5	$ 5	$ 5
Balance at end of period (in shares)		330.6	334.1	348.7	354.8	330.6	348.7
Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period	$ 5,729	$ 5,706	$ 5,814	$ 5,685	$ 5,770	$ 5,814	$ 5,770
Share-based compensation plans		23	(108)	43	(85)
Balance at end of period		5,729	5,706	5,728	5,685	5,729	5,728
Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period	9,292	9,219	8,982	7,920	7,391	8,982	7,391
Net income		232	375	667	420
Dividends		(159)	(139)	(145)	(118)
Balance at end of period		9,292	9,219	8,442	7,920	9,292	8,442
Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period	(13,460)	(12,967)	(12,185)	(10,163)	(9,418)	(12,185)	(9,418)
Share-based compensation plans		7	46	2	37
Purchase of treasury stock		(500)	(828)	(850)	(782)
Balance at end of period		(13,460)	(12,967)	(11,011)	(10,163)	(13,460)	(11,011)
Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period	(326)	(360)	(391)	141	(17)	(391)	(17)
Other comprehensive income		34	31	(385)	162
Balance at end of period		$ (326)	$ (360)	$ (244)	$ 141	$ (326)	$ (244)
Adoption of ASU 2016-02
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU								$ 1
Adoption of ASU 2016-02 \| Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU								0
Adoption of ASU 2016-02 \| Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU								0
Adoption of ASU 2016-02 \| Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU								1
Adoption of ASU 2016-02 \| Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU								0
Adoption of ASU 2016-02 \| Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU								$ 0
Adoption of ASU 2014-09
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										$ (149)
Balance at beginning of period (as adjusted)										3,582
Adoption of ASU 2014-09 \| Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Balance at beginning of period (in shares)					359.1		359.1
Adoption of ASU										0
Balance at beginning of period (as adjusted)										5
Adoption of ASU 2014-09 \| Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Balance at beginning of period (as adjusted)										5,770
Adoption of ASU 2014-09 \| Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										(149)
Balance at beginning of period (as adjusted)										7,242
Adoption of ASU 2014-09 \| Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Balance at beginning of period (as adjusted)										(9,418)
Adoption of ASU 2014-09 \| Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Balance at beginning of period (as adjusted)										(17)
Adoption of ASU 2016-01
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-01 \| Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-01 \| Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-01 \| Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										4
Adoption of ASU 2016-01 \| Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-01 \| Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										(4)
Adoption of ASU 2016-16
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										372
Adoption of ASU 2016-16 \| Class A Common Stock
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-16 \| Additional Paid-in- Capital
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-16 \| Retained Earnings
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										372
Adoption of ASU 2016-16 \| Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										0
Adoption of ASU 2016-16 \| Accumulated Other Comprehensive Loss
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Adoption of ASU										$ 0
Subsequent Even \| Treasury Stock, at Cost
(Increase) Decrease in Shareholders' Deficit [Roll Forward]
Purchase of treasury stock	$ (100)