Income Taxes (Tables)

6 Months Ended

Sep. 30, 2019

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 21% U.S. federal statutory rate for income taxes were as follows:

	Six Months Ended September 30,
	2019			2018
	(in millions)
Income tax benefit (expense) at the federal statutory rate	$	101		$	(93	)
Effect of:
State income taxes, net of federal income tax effect	18			(34		)
State law changes, net of federal income tax effect	(1		)	59
Increase deferred tax liability for organizational restructuring	(4		)	(13		)
Credit for increasing research activities	6			11
Change in federal and state valuation allowance	(37		)	11
Other, net	3			(5		)
Income tax benefit (expense)	$	86		$	(64	)
Effective income tax rate	18.0		%	14.4		%