Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2016
Income Tax Disclosure [Line Items]
Effective tax rate	39.00%	38.00%	37.00%	37.00%
(Benefit) provision for income taxes	$ (29)	$ 210	$ 212	$ 441
Deferred tax assets	1,100		1,100		$ 1,900
Net deferred income tax liability	$ 8,065		$ 8,065		$ 8,016
Federal [Member]
Income Tax Disclosure [Line Items]
Expiration Dates			Mar. 31, 2035