Related Party Transactions (Brightstar) (Details) - Brightstar [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Related Party Transaction [Line Items]
Accounts receivable	$ 239		$ 239		$ 430
Accounts payable	46		46		$ 96
Revenue from Related Parties	598	$ 1,030	1,375	$ 1,149
Related Party Costs	$ 601	$ 1,071	$ 1,362	$ 1,165