Related Party Transactions (Brightstar) (Details) - Brightstar [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015
Related Party Transaction [Line Items]
Accounts receivable	$ 264		$ 264		$ 430
Accounts payable	57		57		$ 96
Revenue from Related Parties	402	$ 102	777	$ 119
Related Party Costs	$ 343	$ 78	$ 761	$ 94