Supplemental Guarantor Information (Balance Sheet) (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Current assets
Cash and cash equivalents	$ 628,000,000	$ 509,000,000	$ 301,000,000	$ 317,000,000
Accounts receivable, net
— third parties	1,289,000,000	1,382,000,000
— related parties	53,000,000	54,000,000
Inventories	1,431,000,000	1,173,000,000
Prepaid expenses and other current assets	112,000,000	101,000,000
Fair value of derivative instruments	77,000,000	51,000,000
Deferred income tax assets	79,000,000	101,000,000
Assets held for sale	6,000,000	102,000,000
Total current assets	3,675,000,000	3,473,000,000
Property, plant and equipment, net	3,542,000,000	3,513,000,000
Goodwill	607,000,000	611,000,000
Intangible assets, net	584,000,000	640,000,000
Investment in and advances to non–consolidated affiliates	447,000,000	612,000,000
Investments in consolidated subsidiaries	0	0
Deferred income tax assets	95,000,000	80,000,000
Other long–term assets
— third parties	137,000,000	173,000,000
— related parties	15,000,000	12,000,000
Total assets	9,102,000,000	9,114,000,000
Current liabilities
Current portion of long–term debt	108,000,000	92,000,000
Short-term borrowings
— third parties	846,000,000	723,000,000
— related parties	0	0
Accounts payable
— third parties	1,854,000,000	1,418,000,000
— related parties	44,000,000	53,000,000
Fair value of derivative instruments	149,000,000	60,000,000
Accrued expenses and other current liabilities
— third parties	572,000,000	547,000,000
— related party	0	250,000,000
Deferred income tax liabilities	20,000,000	16,000,000
Liabilities held for sale	0	11,000,000
Total current liabilities	3,593,000,000	3,170,000,000
Long-term debt, net of current portion
— third parties	4,349,000,000	4,359,000,000
— related parties	0	0
Deferred income tax liabilities	261,000,000	425,000,000
Accrued postretirement benefits	748,000,000	621,000,000
Other long–term liabilities	221,000,000	271,000,000
Total liabilities	9,172,000,000	8,846,000,000
Commitments and contingencies
Temporary equity - intercompany	0	0
Shareholder’s (deficit) equity
Common stock	0	0
Additional paid–in capital	1,404,000,000	1,404,000,000
(Accumulated deficit) retained earnings	(925,000,000)	(1,073,000,000)
Accumulated other comprehensive (loss) income	(561,000,000)	(91,000,000)	(268,000,000)	(191,000,000)
Total (deficit) equity of our common shareholder	(82,000,000)	240,000,000
Noncontrolling interests	12,000,000	28,000,000
Total (deficit) equity	(70,000,000)	268,000,000	239,000,000	123,000,000
Total liabilities and (deficit) equity	9,102,000,000	9,114,000,000
Parent [Member]
Current assets
Cash and cash equivalents	4,000,000	4,000,000	4,000,000	6,000,000
Accounts receivable, net
— third parties	23,000,000	15,000,000
— related parties	385,000,000	1,093,000,000
Inventories	55,000,000	36,000,000
Prepaid expenses and other current assets	6,000,000	5,000,000
Fair value of derivative instruments	19,000,000	12,000,000
Deferred income tax assets	0	0
Assets held for sale	0	28,000,000
Total current assets	492,000,000	1,193,000,000
Property, plant and equipment, net	95,000,000	100,000,000
Goodwill	0	0
Intangible assets, net	19,000,000	19,000,000
Investment in and advances to non–consolidated affiliates	0	0
Investments in consolidated subsidiaries	3,013,000,000	3,273,000,000
Deferred income tax assets	0	0
Other long–term assets
— third parties	57,000,000	73,000,000
— related parties	1,265,000,000	844,000,000
Total assets	4,941,000,000	5,502,000,000
Current liabilities
Current portion of long–term debt	22,000,000	21,000,000
Short-term borrowings
— third parties	394,000,000	367,000,000
— related parties	0	32,000,000
Accounts payable
— third parties	27,000,000	35,000,000
— related parties	78,000,000	89,000,000
Fair value of derivative instruments	83,000,000	14,000,000
Accrued expenses and other current liabilities
— third parties	99,000,000	104,000,000
— related party	0	250,000,000
Deferred income tax liabilities	0	0
Liabilities held for sale		10,000,000
Total current liabilities	703,000,000	922,000,000
Long-term debt, net of current portion
— third parties	4,205,000,000	4,219,000,000
— related parties	49,000,000	49,000,000
Deferred income tax liabilities	0	0
Accrued postretirement benefits	30,000,000	44,000,000
Other long–term liabilities	36,000,000	28,000,000
Total liabilities	5,023,000,000	5,262,000,000
Commitments and contingencies
Temporary equity - intercompany	0	0
Shareholder’s (deficit) equity
Common stock	0	0
Additional paid–in capital	1,404,000,000	1,404,000,000
(Accumulated deficit) retained earnings	(925,000,000)	(1,073,000,000)
Accumulated other comprehensive (loss) income	(561,000,000)	(91,000,000)
Total (deficit) equity of our common shareholder	(82,000,000)	240,000,000
Noncontrolling interests	0	0
Total (deficit) equity	(82,000,000)	240,000,000
Total liabilities and (deficit) equity	4,941,000,000	5,502,000,000
Guarantors [Member]
Current assets
Cash and cash equivalents	365,000,000	372,000,000	196,000,000	215,000,000
Accounts receivable, net
— third parties	1,034,000,000	1,121,000,000
— related parties	154,000,000	193,000,000
Inventories	1,084,000,000	880,000,000
Prepaid expenses and other current assets	89,000,000	76,000,000
Fair value of derivative instruments	55,000,000	26,000,000
Deferred income tax assets	70,000,000	96,000,000
Assets held for sale	6,000,000	74,000,000
Total current assets	2,857,000,000	2,838,000,000
Property, plant and equipment, net	2,549,000,000	2,485,000,000
Goodwill	596,000,000	600,000,000
Intangible assets, net	562,000,000	617,000,000
Investment in and advances to non–consolidated affiliates	447,000,000	612,000,000
Investments in consolidated subsidiaries	597,000,000	612,000,000
Deferred income tax assets	47,000,000	28,000,000
Other long–term assets
— third parties	70,000,000	89,000,000
— related parties	64,000,000	61,000,000
Total assets	7,789,000,000	7,942,000,000
Current liabilities
Current portion of long–term debt	8,000,000	10,000,000
Short-term borrowings
— third parties	381,000,000	287,000,000
— related parties	122,000,000	809,000,000
Accounts payable
— third parties	1,195,000,000	912,000,000
— related parties	393,000,000	377,000,000
Fair value of derivative instruments	62,000,000	40,000,000
Accrued expenses and other current liabilities
— third parties	412,000,000	358,000,000
— related party	47,000,000	4,000,000
Deferred income tax liabilities	20,000,000	16,000,000
Liabilities held for sale		1,000,000
Total current liabilities	2,640,000,000	2,814,000,000
Long-term debt, net of current portion
— third parties	28,000,000	40,000,000
— related parties	1,209,000,000	788,000,000
Deferred income tax liabilities	254,000,000	419,000,000
Accrued postretirement benefits	534,000,000	422,000,000
Other long–term liabilities	175,000,000	236,000,000
Total liabilities	4,840,000,000	4,719,000,000
Commitments and contingencies
Temporary equity - intercompany	1,681,000,000	1,681,000,000
Shareholder’s (deficit) equity
Common stock	0	0
Additional paid–in capital	0	0
(Accumulated deficit) retained earnings	1,831,000,000	1,684,000,000
Accumulated other comprehensive (loss) income	(563,000,000)	(142,000,000)
Total (deficit) equity of our common shareholder	1,268,000,000	1,542,000,000
Noncontrolling interests	0	0
Total (deficit) equity	1,268,000,000	1,542,000,000
Total liabilities and (deficit) equity	7,789,000,000	7,942,000,000
Non-Guarantors [Member]
Current assets
Cash and cash equivalents	259,000,000	133,000,000	101,000,000	96,000,000
Accounts receivable, net
— third parties	232,000,000	246,000,000
— related parties	158,000,000	57,000,000
Inventories	294,000,000	257,000,000
Prepaid expenses and other current assets	17,000,000	20,000,000
Fair value of derivative instruments	9,000,000	14,000,000
Deferred income tax assets	9,000,000	5,000,000
Assets held for sale	0	0
Total current assets	978,000,000	732,000,000
Property, plant and equipment, net	898,000,000	928,000,000
Goodwill	11,000,000	11,000,000
Intangible assets, net	3,000,000	4,000,000
Investment in and advances to non–consolidated affiliates	0	0
Investments in consolidated subsidiaries	0	0
Deferred income tax assets	48,000,000	52,000,000
Other long–term assets
— third parties	10,000,000	11,000,000
— related parties	0	0
Total assets	1,948,000,000	1,738,000,000
Current liabilities
Current portion of long–term debt	78,000,000	61,000,000
Short-term borrowings
— third parties	71,000,000	69,000,000
— related parties	0	0
Accounts payable
— third parties	632,000,000	471,000,000
— related parties	42,000,000	29,000,000
Fair value of derivative instruments	10,000,000	7,000,000
Accrued expenses and other current liabilities
— third parties	61,000,000	85,000,000
— related party	6,000,000	2,000,000
Deferred income tax liabilities	0	0
Liabilities held for sale		0
Total current liabilities	900,000,000	724,000,000
Long-term debt, net of current portion
— third parties	116,000,000	100,000,000
— related parties	56,000,000	56,000,000
Deferred income tax liabilities	7,000,000	6,000,000
Accrued postretirement benefits	184,000,000	155,000,000
Other long–term liabilities	10,000,000	7,000,000
Total liabilities	1,273,000,000	1,048,000,000
Commitments and contingencies
Temporary equity - intercompany	0	0
Shareholder’s (deficit) equity
Common stock	0	0
Additional paid–in capital	0	0
(Accumulated deficit) retained earnings	711,000,000	680,000,000
Accumulated other comprehensive (loss) income	(48,000,000)	(18,000,000)
Total (deficit) equity of our common shareholder	663,000,000	662,000,000
Noncontrolling interests	12,000,000	28,000,000
Total (deficit) equity	675,000,000	690,000,000
Total liabilities and (deficit) equity	1,948,000,000	1,738,000,000
Eliminations [Member]
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net
— third parties	0	0
— related parties	(644,000,000)	(1,289,000,000)
Inventories	(2,000,000)	0
Prepaid expenses and other current assets	0	0
Fair value of derivative instruments	(6,000,000)	(1,000,000)
Deferred income tax assets	0	0
Assets held for sale	0	0
Total current assets	(652,000,000)	(1,290,000,000)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Investment in and advances to non–consolidated affiliates	0	0
Investments in consolidated subsidiaries	(3,610,000,000)	(3,885,000,000)
Deferred income tax assets	0	0
Other long–term assets
— third parties	0	0
— related parties	(1,314,000,000)	(893,000,000)
Total assets	(5,576,000,000)	(6,068,000,000)
Current liabilities
Current portion of long–term debt	0	0
Short-term borrowings
— third parties	0	0
— related parties	(122,000,000)	(841,000,000)
Accounts payable
— third parties	0	0
— related parties	(469,000,000)	(442,000,000)
Fair value of derivative instruments	(6,000,000)	(1,000,000)
Accrued expenses and other current liabilities
— third parties	0	0
— related party	(53,000,000)	(6,000,000)
Deferred income tax liabilities	0	0
Liabilities held for sale		0
Total current liabilities	(650,000,000)	(1,290,000,000)
Long-term debt, net of current portion
— third parties	0	0
— related parties	(1,314,000,000)	(893,000,000)
Deferred income tax liabilities	0	0
Accrued postretirement benefits	0	0
Other long–term liabilities	0	0
Total liabilities	(1,964,000,000)	(2,183,000,000)
Commitments and contingencies
Temporary equity - intercompany	(1,681,000,000)	(1,681,000,000)
Shareholder’s (deficit) equity
Common stock	0	0
Additional paid–in capital	0	0
(Accumulated deficit) retained earnings	(2,542,000,000)	(2,364,000,000)
Accumulated other comprehensive (loss) income	611,000,000	160,000,000
Total (deficit) equity of our common shareholder	(1,931,000,000)	(2,204,000,000)
Noncontrolling interests	0	0
Total (deficit) equity	(1,931,000,000)	(2,204,000,000)
Total liabilities and (deficit) equity	$ (5,576,000,000)	$ (6,068,000,000)