Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (445)	$ 1,372		$ 1,372
Other comprehensive income (loss)	57	(124)	$ 66	(67)	$ 18
Net other comprehensive items	(388)	(449)
Less: Noncontrolling interest	1	(4)
Ending Balance	1,398	(445)		1,398
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(348)	(227)		(227)
Other comprehensive income (loss)	56	(125)
Net other comprehensive items	(292)	(352)
Less: Noncontrolling interest	1	(4)
Ending Balance	(293)	(348)		(293)
Unrealized Gains on Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	2	2		2
Net other comprehensive items	2	2
Ending Balance	2	2		2
Pension and Other Postretirement Benefit Liability Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(99)	(100)		(100)
Other comprehensive income (loss)	1	1
Net other comprehensive items	(98)	(99)
Ending Balance	(98)	(99)		(98)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance		$ (325)		(325)
Ending Balance	$ (389)			$ (389)