Income Taxes (Tables)

9 Months Ended

Dec. 31, 2015

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 vary from the 35% U.S. federal statutory rate for income taxes were as follows:

	Nine Months Ended December 31,
	2015			2014
	(in millions)
Income tax benefit at the federal statutory rate	$	460		$	1,303
Effect of:
State income taxes, net of federal income tax effect	33			96
State law changes, net of federal income tax effect	23			—
Change in federal and state valuation allowance	(647		)	(797		)
Other, net	5			(1		)
Income tax (expense) benefit	$	(126	)	$	601
Effective income tax rate	(9.6		)%	16.1		%