SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION CF (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash Flow [Line Items]
Net cash provided by (used in) operating activities	$ 134,898	$ 116,993
Capital expenditures	(113,405)	(149,262)
Proceeds from asset dispositions	96,376	12,040
Investment in unconsolidated affiliate	7,153	0
Net cash used in investing activities	(24,182)	(137,222)
Proceeds from borrowings	0	88,493
Repayment of debt	(24,300)	(32,518)
Dividends paid	(14,297)	(10,833)
Increases (decreases) in cash related to intercompany advances and debt	0	0
Partial Prepayment Of Put Call Obligation	(33)	(31)
Acquisition of noncontrolling interest	0	(262)
Issuance of Common Stock	7,869	1,629
Tax benefit related to stock-based compensation	433	109
Net cash provided by (used in) financing activities	(30,328)	46,587
Effect of exchange rate changes on cash and cash equivalents	6,411	(2,440)
Net increase (decrease) in cash and cash equivalents	86,799	23,918
Cash and cash equivalents at beginning of period	261,550	116,361
Cash and cash equivalents at end of period	348,349	140,279
Parent Company [Member]
Cash Flow [Line Items]
Net cash provided by (used in) operating activities	(20,075)	(18,520)
Capital expenditures	(8,353)	(418)
Proceeds from asset dispositions	0	0
Investment in unconsolidated affiliate	7,153
Net cash used in investing activities	(15,506)	(418)
Proceeds from borrowings		87,800
Repayment of debt	(24,300)	(30,000)
Dividends paid	(2,742)	40,564
Increases (decreases) in cash related to intercompany advances and debt	112,427	(22,056)
Partial Prepayment Of Put Call Obligation	(33)	(31)
Acquisition of noncontrolling interest		0
Issuance of Common Stock	7,869	1,629
Tax benefit related to stock-based compensation	433	109
Net cash provided by (used in) financing activities	93,654	78,015
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	58,073	59,077
Cash and cash equivalents at beginning of period	76,609	24,075
Cash and cash equivalents at end of period	134,682	83,152
Guarantor Subsidiaries [Member]
Cash Flow [Line Items]
Net cash provided by (used in) operating activities	62,030	60,830
Capital expenditures	(46,389)	(78,620)
Proceeds from asset dispositions	35,185	8,129
Investment in unconsolidated affiliate	0
Net cash used in investing activities	(11,204)	(70,491)
Proceeds from borrowings		0
Repayment of debt	0	0
Dividends paid	(9,755)	(24,927)
Increases (decreases) in cash related to intercompany advances and debt	(40,697)	32,153
Partial Prepayment Of Put Call Obligation	0	0
Acquisition of noncontrolling interest		(262)
Issuance of Common Stock	0	0
Tax benefit related to stock-based compensation	0	0
Net cash provided by (used in) financing activities	(50,452)	6,964
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	374	(2,697)
Cash and cash equivalents at beginning of period	3,155	5,233
Cash and cash equivalents at end of period	3,529	2,536
Non-Guarantor Subsidiaries [Member]
Cash Flow [Line Items]
Net cash provided by (used in) operating activities	92,943	74,683
Capital expenditures	(83,252)	(70,224)
Proceeds from asset dispositions	85,780	3,911
Investment in unconsolidated affiliate	0
Net cash used in investing activities	2,528	(66,313)
Proceeds from borrowings		693
Repayment of debt	0	(2,518)
Dividends paid	(1,800)	(26,470)
Increases (decreases) in cash related to intercompany advances and debt	(71,730)	(10,097)
Partial Prepayment Of Put Call Obligation	0	0
Acquisition of noncontrolling interest		0
Issuance of Common Stock	0	0
Tax benefit related to stock-based compensation	0	0
Net cash provided by (used in) financing activities	(73,530)	(38,392)
Effect of exchange rate changes on cash and cash equivalents	6,411	(2,440)
Net increase (decrease) in cash and cash equivalents	28,352	(32,462)
Cash and cash equivalents at beginning of period	181,786	87,053
Cash and cash equivalents at end of period	210,138	54,591
Consolidations, Eliminations [Member]
Cash Flow [Line Items]
Net cash provided by (used in) operating activities	0	0
Capital expenditures	24,589	0
Proceeds from asset dispositions	(24,589)	0
Investment in unconsolidated affiliate	0
Net cash used in investing activities	0	0
Proceeds from borrowings		0
Repayment of debt	0	0
Dividends paid	0	0
Increases (decreases) in cash related to intercompany advances and debt	0	0
Partial Prepayment Of Put Call Obligation	0	0
Acquisition of noncontrolling interest		0
Issuance of Common Stock	0	0
Tax benefit related to stock-based compensation	0	0
Net cash provided by (used in) financing activities	0	0
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0