Accounts Receivable (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Receivables [Abstract]
Trade accounts receivable	$ 1,158	$ 1,303
Other accounts receivable	134	83
Accounts receivable — third parties	1,292	1,386
Allowance for doubtful accounts — third parties	(3)	(4)	(3)	(5)
Accounts receivable, net — third parties	1,289	1,382
Accounts receivable, net — related parties	$ 53	$ 54