SEGMENT INFORMATION (Details) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013
Segment Reporting Information [Line Items]
Total segment gross revenue	$ 417,328,000	$ 365,754,000	$ 816,322,000	$ 728,362,000
Total consolidated gross revenue	417,328,000	365,754,000	816,322,000	728,362,000
Total earnings from unconsolidated affiliates, net of losses - equity method investments	3,088,000	6,994,000	15,060,000	8,983,000
Gain (loss) on disposal of assets	(3,064,000)	(1,262,000)	(4,785,000)	(6,577,000)
Total consolidated operating income	53,935,000	47,328,000	110,054,000	87,321,000
Total depreciation and amortization	23,858,000	23,321,000	46,677,000	44,693,000
Total identifiable assets	3,165,992,000		3,165,992,000		2,950,692,000
Total investments in unconsolidated affiliates - equity method	265,148,000		265,148,000		265,837,000
Construction in progress within property and equipment	336,700,000		336,700,000		222,800,000
External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	417,328,000	365,754,000	816,322,000	728,362,000
Total consolidated gross revenue	417,328,000	365,754,000	816,322,000	728,362,000
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	1,219,000	647,000	2,066,000	1,026,000
Total consolidated gross revenue	1,219,000	647,000	2,066,000	1,026,000
Corporate And Other [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	19,876,000	9,718,000	38,088,000	17,348,000
Total consolidated gross revenue	19,876,000	9,718,000	38,088,000	17,348,000
Total business unit operating income	(14,516,000)	(15,161,000)	(25,795,000)	(28,231,000)
Total depreciation and amortization	666,000	915,000	1,319,000	1,799,000
Total identifiable assets	497,970,000		497,970,000		388,894,000
Corporate And Other [Member] | External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	18,666,000	9,127,000	36,015,000	16,637,000
Total consolidated gross revenue	18,666,000	9,127,000	36,015,000	16,637,000
Corporate And Other [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	1,210,000	591,000	2,073,000	711,000
Total consolidated gross revenue	1,210,000	591,000	2,073,000	711,000
Europe [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	185,743,000	154,113,000	352,452,000	308,133,000
Total consolidated gross revenue	185,743,000	154,113,000	352,452,000	308,133,000
Total earnings from unconsolidated affiliates, net of losses - equity method investments	873,000	2,368,000	3,913,000	4,374,000
Total business unit operating income	32,958,000	27,008,000	52,979,000	48,884,000
Total depreciation and amortization	8,206,000	8,444,000	15,454,000	16,008,000
Total identifiable assets	933,274,000		933,274,000		808,568,000
Total investments in unconsolidated affiliates - equity method	0		0		8,569,000
Europe [Member] | External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	185,743,000	154,111,000	352,452,000	308,068,000
Total consolidated gross revenue	185,743,000	154,111,000	352,452,000	308,068,000
Europe [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	0	2,000	0	65,000
Total consolidated gross revenue	0	2,000	0	65,000
West Africa [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	79,488,000	68,217,000	158,869,000	138,671,000
Total consolidated gross revenue	79,488,000	68,217,000	158,869,000	138,671,000
Total business unit operating income	18,231,000	13,430,000	37,484,000	29,561,000
Total depreciation and amortization	3,435,000	3,051,000	6,695,000	6,193,000
Total identifiable assets	425,553,000		425,553,000		390,402,000
West Africa [Member] | External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	79,488,000	68,217,000	158,869,000	138,671,000
Total consolidated gross revenue	79,488,000	68,217,000	158,869,000	138,671,000
West Africa [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	0	0	0	0
Total consolidated gross revenue	0	0	0	0
North America [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	60,727,000	57,375,000	119,293,000	110,281,000
Total consolidated gross revenue	60,727,000	57,375,000	119,293,000	110,281,000
Total earnings from unconsolidated affiliates, net of losses - equity method investments	112,000	0	104,000	0
Total business unit operating income	9,164,000	6,130,000	17,287,000	12,605,000
Total depreciation and amortization	6,057,000	3,107,000	12,196,000	6,373,000
Total identifiable assets	513,223,000		513,223,000		527,710,000
Total investments in unconsolidated affiliates - equity method	60,621,000		60,621,000		60,517,000
North America [Member] | External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	60,718,000	57,321,000	119,300,000	110,031,000
Total consolidated gross revenue	60,718,000	57,321,000	119,300,000	110,031,000
North America [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	9,000	54,000	(7,000)	250,000
Total consolidated gross revenue	9,000	54,000	(7,000)	250,000
Australia [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	40,466,000	44,839,000	84,464,000	89,341,000
Total consolidated gross revenue	40,466,000	44,839,000	84,464,000	89,341,000
Total business unit operating income	2,508,000	6,829,000	5,788,000	13,338,000
Total depreciation and amortization	1,908,000	2,504,000	3,797,000	4,987,000
Total identifiable assets	214,234,000		214,234,000		245,757,000
Australia [Member] | External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	40,466,000	44,839,000	84,464,000	89,341,000
Total consolidated gross revenue	40,466,000	44,839,000	84,464,000	89,341,000
Australia [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	0	0	0	0
Total consolidated gross revenue	0	0	0	0
Other International [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	32,247,000	32,139,000	65,222,000	65,614,000
Total consolidated gross revenue	32,247,000	32,139,000	65,222,000	65,614,000
Total earnings from unconsolidated affiliates, net of losses - equity method investments	2,103,000	4,626,000	11,043,000	4,609,000
Total business unit operating income	8,654,000	10,354,000	27,096,000	17,741,000
Total depreciation and amortization	3,586,000	5,300,000	7,216,000	9,333,000
Total identifiable assets	581,738,000		581,738,000		589,361,000
Total investments in unconsolidated affiliates - equity method	204,527,000		204,527,000		196,751,000
Other International [Member] | External Customer [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	32,247,000	32,139,000	65,222,000	65,614,000
Total consolidated gross revenue	32,247,000	32,139,000	65,222,000	65,614,000
Other International [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total segment gross revenue	0	0	0	0
Total consolidated gross revenue	$ 0	$ 0	$ 0	$ 0