Income Taxes (Tables)

9 Months Ended

Dec. 31, 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:

	Nine Months Ended December 31,
	2019			2018
	(in millions)
Income tax benefit (expense) at the federal statutory rate	$	212		$	(61	)
Effect of:
State income taxes, net of federal income tax effect	39			(40		)
State law changes, net of federal income tax effect	6			62
Increase deferred tax liability for organizational restructuring	(4		)	(12		)
Credit for increasing research activities	9			13
Change in federal and state valuation allowance	236			12
Increase in liability for unrecognized tax benefits	(4		)	(6		)
Non-deductible penalties	—			(29		)
Other, net	—			5
Income tax benefit (expense)	$	494		$	(56	)
Effective income tax rate	49.0		%	19.2		%