Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017
Income Tax Disclosure [Line Items]
Effective tax rate	37.00%	38.00%
Provision for income taxes	$ 96	$ 146
Deferred tax assets	1,900		$ 1,000
Net deferred income tax liability	$ 8,100		$ 7,900
Federal [Member]
Income Tax Disclosure [Line Items]
Expiration Dates	Mar. 31, 2038