Supplemental Guarantor Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Supplemental guarantor information statements of operation
Net sales	$ 2,831	$ 2,414	$ 5,511	$ 4,815
Cost of goods sold (exclusive of depreciation and amortization)	2,483	2,074	4,812	4,172
Selling, general and administrative expenses	103	109	211	229
Depreciation and amortization	90	79	179	156
Research and development expenses	12	12	24	22
Interest expense and amortization of debt issuance costs	82	75	163	151
Gain on assets held for sale	0	0	(11)	0
Restructuring and impairment, net	7	18	13	27
Equity in net loss of non-consolidated affiliates	0	3	2	7
Equity in net (income) loss of consolidated subsidiaries		0	0	0
Other (income) expense, net	18	(5)	23	(15)
Total expenses	2,795	2,365	5,416	4,749
Income before income taxes	36	49	95	66
Income tax provision	(2)	26	22	29
Net income	38	23	73	37
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to our common shareholder	38	23	73	37
Comprehensive income (loss)	(98)	184	(31)	155
Less: Comprehensive loss attributable to noncontrolling interest	(2)	(1)	(1)	(2)
Comprehensive income (loss) attributable to our common shareholder	(96)	185	(30)	157
Parent [Member]
Supplemental guarantor information statements of operation
Net sales	166	163	340	341
Cost of goods sold (exclusive of depreciation and amortization)	172	140	344	329
Selling, general and administrative expenses	(1)	8	(5)	52
Depreciation and amortization	5	4	9	8
Research and development expenses	0	0	0	1
Interest expense and amortization of debt issuance costs	81	78	161	157
Gain on assets held for sale			(5)
Restructuring and impairment, net	0	1	0	1
Equity in net loss of non-consolidated affiliates	(128)	0	0	0
Equity in net (income) loss of consolidated subsidiaries		(80)	(218)	(235)
Other (income) expense, net	(2)	(12)	(22)	(10)
Total expenses	127	139	264	303
Income before income taxes	39	24	76	38
Income tax provision	1	1	3	1
Net income	38	23	73	37
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to our common shareholder	38	23	73	37
Comprehensive income (loss)	(96)	185	(30)	157
Less: Comprehensive loss attributable to noncontrolling interest	0	0	0	0
Comprehensive income (loss) attributable to our common shareholder	(96)	185	(30)	157
Guarantors [Member]
Supplemental guarantor information statements of operation
Net sales	2,415	1,979	4,650	3,941
Cost of goods sold (exclusive of depreciation and amortization)	2,121	1,729	4,071	3,446
Selling, general and administrative expenses	83	82	174	145
Depreciation and amortization	65	60	129	118
Research and development expenses	11	11	23	20
Interest expense and amortization of debt issuance costs	20	8	34	15
Gain on assets held for sale			(6)
Restructuring and impairment, net	6	17	11	25
Equity in net loss of non-consolidated affiliates	(10)	3	2	7
Equity in net (income) loss of consolidated subsidiaries		(23)	(19)	(49)
Other (income) expense, net	(1)	(6)	3	(35)
Total expenses	2,295	1,881	4,422	3,692
Income before income taxes	120	98	228	249
Income tax provision	(6)	18	12	16
Net income	126	80	216	233
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to our common shareholder	126	80	216	233
Comprehensive income (loss)	32	184	106	356
Less: Comprehensive loss attributable to noncontrolling interest	0	0	0	0
Comprehensive income (loss) attributable to our common shareholder	32	184	106	356
Non-Guarantor [Member]
Supplemental guarantor information statements of operation
Net sales	684	599	1,369	1,225
Cost of goods sold (exclusive of depreciation and amortization)	626	532	1,247	1,089
Selling, general and administrative expenses	21	19	42	32
Depreciation and amortization	20	15	41	30
Research and development expenses	1	1	1	1
Interest expense and amortization of debt issuance costs	2	(1)	5	(2)
Gain on assets held for sale			0
Restructuring and impairment, net	1	0	2	1
Equity in net loss of non-consolidated affiliates	0	0	0	0
Equity in net (income) loss of consolidated subsidiaries		0	0	0
Other (income) expense, net	0	3	5	11
Total expenses	671	569	1,343	1,162
Income before income taxes	13	30	26	63
Income tax provision	3	7	7	12
Net income	10	23	19	51
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to our common shareholder	10	23	19	51
Comprehensive income (loss)	(19)	75	25	81
Less: Comprehensive loss attributable to noncontrolling interest	(2)	(1)	(1)	(2)
Comprehensive income (loss) attributable to our common shareholder	(17)	76	26	83
Eliminations [Member]
Supplemental guarantor information statements of operation
Net sales	(434)	(327)	(848)	(692)
Cost of goods sold (exclusive of depreciation and amortization)	(436)	(327)	(850)	(692)
Selling, general and administrative expenses	0	0	0	0
Depreciation and amortization	0	0	0	0
Research and development expenses	0	0	0	0
Interest expense and amortization of debt issuance costs	(21)	(10)	(37)	(19)
Gain on assets held for sale			0
Restructuring and impairment, net	0	0	0	0
Equity in net loss of non-consolidated affiliates	138	0	0	0
Equity in net (income) loss of consolidated subsidiaries		103	237	284
Other (income) expense, net	21	10	37	19
Total expenses	(298)	(224)	(613)	(408)
Income before income taxes	(136)	(103)	(235)	(284)
Income tax provision	0	0	0	0
Net income	(136)	(103)	(235)	(284)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to our common shareholder	(136)	(103)	(235)	(284)
Comprehensive income (loss)	(15)	(260)	(132)	(439)
Less: Comprehensive loss attributable to noncontrolling interest	0	0	0	0
Comprehensive income (loss) attributable to our common shareholder	$ (15)	$ (260)	$ (132)	$ (439)