Components of Equity (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stockholders Equity Note [Line Items]
Beginning Balance	$ 7,070	$ 7,520	$ 7,325	$ 7,566
Net income (loss)	(352)	286	(355)	472
Net income (loss)	(353)	287	(356)	474
Issuance of common stock for comprehensive stock plans, net	6	4	1	2
Repurchase of common stock		(200)	(147)	(200)
Dividends declared on common stock		(145)	(141)	(294)
Distributions to non-controlling interests				(67)
Changes in ownership and other	1	5	58	(10)
Other comprehensive income/(loss)	(2)	3	(18)	3
Ending Balance	6,722	7,474	6,722	7,474
Common Stock
Stockholders Equity Note [Line Items]
Beginning Balance	7	7	7	7
Ending Balance	7	7	7	7
Additional Paid-in Capital
Stockholders Equity Note [Line Items]
Beginning Balance	7,580	8,138	7,675	8,156
Issuance of common stock for comprehensive stock plans, net	6	4	1	2
Repurchase of common stock		(200)	(147)	(200)
Changes in ownership and other		6	57	(10)
Ending Balance	7,586	7,948	7,586	7,948
Accumulated Other Comprehensive Income (Loss)
Stockholders Equity Note [Line Items]
Beginning Balance	(72)	(59)	(56)	(59)
Other comprehensive income/(loss)	(2)	3	(18)	3
Ending Balance	(74)	(56)	(74)	(56)
Retained Earnings / (Deficit)
Stockholders Equity Note [Line Items]
Beginning Balance	(451)	(573)	(307)	(610)
Net income (loss)	(352)	286	(355)	472
Dividends declared on common stock		(145)	(141)	(294)
Changes in ownership and other	1		1
Ending Balance	(802)	(432)	(802)	(432)
Non-redeemable, non-controlling interests
Stockholders Equity Note [Line Items]
Beginning Balance	6	7	6	72
Net income attributable to non-controlling interests	(1)	1	(1)	2
Distributions to non-controlling interests				(67)
Changes in ownership and other		(1)
Ending Balance	5	7	5	7
Redeemable, non-controlling interests
Stockholders Equity Note [Line Items]
Beginning Balance	84	147	142	128
Net income	(3)	3	(3)	5
Distributions to non-controlling interests		(1)		(3)
Changes in ownership and other		(8)	(56)	11
Ending Balance	$ 81	$ 141	$ 81	$ 141