Postretirement Benefits (Tables) (Other Postretirement Benefit Plan, Defined Benefit [Member])

12 Months Ended

Mar. 31, 2015

Other Postretirement Benefit Plan, Defined Benefit [Member]

Defined Benefit Plan Disclosure [Line Items]

Schedule of Net Periodic Expense (Income) for Postretirement Welfare Benefits

The net periodic expense for our postretirement welfare benefits is as follows:

	Years Ended March 31,
(In millions)	2015			2014			2013
Service cost - benefits earned during the year	$	1		$	2		$	2
Interest cost on accumulated benefit obligation	5			5			6
Amortization of unrecognized actuarial gain and prior service credit	(4		)	(1		)	(2		)
Curtailment gain	—			(2		)	—
Net periodic postretirement expense	$	2		$	4		$	6

Schedule of Changes in Benefit Obligations for Postretirement Welfare Plans

Information regarding the changes in benefit obligations for our postretirement welfare plans is as follows:

	Years Ended March 31,
(In millions)	2015			2014
Benefit obligation at beginning of period	$	119		$	131
Service cost	1			2
Interest cost	5			5
Actuarial loss (gain)	5			(2		)
Benefit payments	(12		)	(15		)
Curtailment gain	—			(2		)
Benefit obligation at end of period	$	118		$	119