SUPPLEMENTAL GUARANTOR AND NON-GUARANTOR CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Condensed consolidating statements of operations
Net sales	$ 6,114,999	$ 6,763,177	$ 18,000,337	$ 18,646,187
Cost of sales	5,698,544	6,310,710	16,864,196	17,444,463
Gross profit	416,455	452,467	1,136,141	1,201,724
Selling, general and administrative expenses	231,551	240,617	715,040	666,798
Intangible amortization	18,734	19,319	62,318	43,117
Interest and other, net	25,928	65,981	86,876	106,363
Income before income taxes	140,242	126,550	271,907	385,446
Provision for (benefit from) income taxes	10,773	(22,360)	39,217	2,709
Equity in earnings in subsidiaries	0	0	0	0
Net income	129,469	148,910	232,690	382,737
Reportable legal entities | Parent
Condensed consolidating statements of operations
Net sales	0	0	0	0
Cost of sales	0	0	0	0
Gross profit	0	0	0	0
Selling, general and administrative expenses	0	0	0	0
Intangible amortization	25	75	175	225
Interest and other, net	(370,703)	49,358	(561,290)	(347,663)
Income before income taxes	370,678	(49,433)	561,115	347,438
Provision for (benefit from) income taxes	0	0	11	0
Equity in earnings in subsidiaries	(241,209)	198,343	(328,414)	35,299
Net income	129,469	148,910	232,690	382,737
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating statements of operations
Net sales	4,186,855	4,597,684	12,008,455	13,126,281
Cost of sales	3,722,516	4,187,076	10,822,629	11,972,388
Gross profit	464,339	410,608	1,185,826	1,153,893
Selling, general and administrative expenses	66,738	83,346	212,059	213,614
Intangible amortization	864	960	2,298	2,881
Interest and other, net	662,422	316,345	1,322,198	929,730
Income before income taxes	(265,685)	9,957	(350,729)	7,668
Provision for (benefit from) income taxes	(4,018)	(8,071)	(947)	(4,630)
Equity in earnings in subsidiaries	(71,920)	(88,988)	(136,175)	(140,241)
Net income	(333,587)	(70,960)	(485,957)	(127,943)
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating statements of operations
Net sales	4,453,753	5,718,182	13,981,899	15,168,232
Cost of sales	4,501,637	5,676,323	14,031,584	15,120,401
Gross profit	(47,884)	41,859	(49,685)	47,831
Selling, general and administrative expenses	164,813	157,271	502,981	453,184
Intangible amortization	17,845	18,284	59,845	40,011
Interest and other, net	(265,791)	(299,722)	(674,032)	(475,704)
Income before income taxes	35,249	166,026	61,521	30,340
Provision for (benefit from) income taxes	14,791	(14,289)	40,153	7,339
Equity in earnings in subsidiaries	4,401	(10,534)	(69,935)	42,225
Net income	24,859	169,781	(48,567)	65,226
Eliminations
Condensed consolidating statements of operations
Net sales	(2,525,609)	(3,552,689)	(7,990,017)	(9,648,326)
Cost of sales	(2,525,609)	(3,552,689)	(7,990,017)	(9,648,326)
Gross profit	0	0	0	0
Selling, general and administrative expenses	0	0	0	0
Intangible amortization	0	0	0	0
Interest and other, net	0	0	0	0
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in earnings in subsidiaries	308,728	(98,821)	534,524	62,717
Net income	$ 308,728	$ (98,821)	$ 534,524	$ 62,717