Stockholders' Equity - Narrative (Details) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2015 $ / shares	Sep. 30, 2015 USD ($) vote $ / shares shares	Sep. 30, 2014 USD ($) $ / shares	Sep. 30, 2015 USD ($) vote $ / shares	Sep. 30, 2014 USD ($) $ / shares	Oct. 29, 2015 USD ($)	May. 31, 2015 USD ($)
Class of Stock [Line Items]
Share of common stock outstanding, vote on proposals | vote		1		1
Dividends per share (in dollars per share) | $ / shares	$ 0.24
Dividends declared per common share (in dollars per share) | $ / shares	$ 0.28	$ 0.28	$ 0.24	$ 0.52	$ 0.48
Authorized amount of company's common stock by board							$ 500,000,000
Amount of shares bought (in shares) | shares		2.5
Average price per share (in dollars per share) | $ / shares		$ 196.20		$ 196.20
Authorized amount available for future repurchases		$ 0		$ 0
Net foreign currency translation gain (loss)		(20,000,000)	$ (139,000,000)	30,000,000	$ (151,000,000)
Net actuarial losses attributable to redeemable noncontrolling interest		(1,000,000)	$ 0	28,000,000	$ 0
Noncontrolling interest
Class of Stock [Line Items]
Net actuarial losses attributable to redeemable noncontrolling interest		$ 0		$ 6,000,000
Subsequent Event
Class of Stock [Line Items]
Authorized amount of company's common stock by board						$ 2,000,000,000