Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2016
Income Tax Disclosure [Line Items]
Effective tax rate	38.00%	34.00%
Provision for income taxes	$ 146	$ 70
Deferred tax assets	1,500		$ 1,900
Net deferred income tax liability	$ 8,170		$ 8,016
Federal [Member]
Income Tax Disclosure [Line Items]
Expiration Dates	Mar. 31, 2035