Goodwill and Intangible Assets, Net - Intangible Assets Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense of intangible assets	$ 444	$ 431	$ 494
Estimated annual amortization expense, 2018	385
Estimated annual amortization expense, 2019	370
Estimated annual amortization expense, 2020	355
Estimated annual amortization expense, 2021	341
Estimated annual amortization expense, 2022	309
Estimated annual amortization expense, after 2022	$ 1,905