Income Taxes (Tables)

6 Months Ended

Sep. 30, 2017

Income Tax Disclosure [Abstract]

Factors Causing Variation in Effective Tax Rate From US Federal Statutory Rate

The differences that caused our effective income tax rates to differ from the 35% U.S. federal statutory rate for income taxes were as follows:

	Six Months Ended September 30,
	2017			2016
	(in millions)
Income tax (expense) benefit at the federal statutory rate	$	(192	)	$	94
Effect of:
State income taxes, net of federal income tax effect	(38		)	5
State law changes, net of federal income tax effect	(27		)	3
Increase deferred tax liability for business activity changes	(65		)	—
Credit for increasing research activities	8			—
Tax benefit from organizational restructuring	—			42
Change in federal and state valuation allowance	(60		)	(314		)
Other, net	(16		)	(5		)
Income tax expense	$	(390	)	$	(175	)
Effective income tax rate	71.2		%	(65.1		)%