Operating Segments (Schedule Of Sales And Long-Lived Assets By Country) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 2,271,801	$ 2,542,115	$ 2,461,699
Long-Lived Assets	404,535	395,999	386,516
United States [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	290,950	304,527	324,285
Long-Lived Assets	70,929	61,347	64,235
Belgium [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	226,562	218,550	203,539
China [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	174,872	210,956	229,112
Germany [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	170,338	173,872	128,144
Poland (Member)
Segment Reporting Information [Line Items]
Sales and other operating revenues	114,765	106,443	126,826
NETHERLANDS
Segment Reporting Information [Line Items]
Sales and other operating revenues	113,297	208,031	174,481
Russia (Member)
Segment Reporting Information [Line Items]
Sales and other operating revenues	126,652	123,114	130,906
Brazil [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	135,980	135,359	137,133
Mozambique [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	55,733	49,543	48,016
All Other Countries [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,054,365	1,196,622	1,144,406
Long-Lived Assets	$ 141,893	$ 149,750	$ 137,132