Trade Accounts Receivable (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Mar. 31, 2014
Components of trade accounts receivable, net    
Accounts receivable - billed $ 614 $ 739
Accounts receivable - unbilled 64 61
Other receivables 8 19
Less: Allowances (17) (19)
Trade accounts receivable, net $ 669 $ 800