Goodwill And Intangible Assets, Net - Narrative - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	12 Months Ended
	Sep. 30, 2015	Mar. 31, 2014	Sep. 30, 2015	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense of intangible assets	$ 109	$ 130	$ 221	$ 259
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Estimated annual amortization expense, 2016	180		180
Estimated annual amortization expense, 2017	382		382
Estimated annual amortization expense, 2018	366		366
Estimated annual amortization expense, 2019	331		331
Estimated annual amortization expense, 2020	304		304
Estimated annual amortization expense, thereafter	$ 1,691		$ 1,691