EMPLOYEE BENEFIT PLANS (Details) (USD $)	3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 number	Sep. 30, 2011	Mar. 31, 2012	Sep. 30, 2012 Plan 2007 [Member]	Jun. 30, 2011 Officer Stock Compensation Expense [Member]	Mar. 31, 2012 UK staff pension plan [Member]	Sep. 30, 2012 UK expatriate pension plan [Member]	Mar. 31, 2013 UK expatriate pension plan [Member]	Sep. 30, 2012 Norway pension plan [Member]	Mar. 31, 2013 Norway pension plan [Member]
Pension Plan [Line Items]
Service cost	$ 2,052,000	$ 1,614,000	$ 4,109,000	$ 3,248,000
Interest cost	6,418,000	7,122,000	12,851,000	14,334,000
Expected return on assets	(7,264,000)	(7,397,000)	(14,545,000)	(14,886,000)
Amortization of unrecognized losses	1,652,000	1,360,000	3,309,000	2,737,000
Net periodic pension cost	2,858,000	2,699,000	5,724,000	5,433,000
Cash Contributions								16,600,000	200,000		4,600,000
Estimated cash contributions										600,000		9,600,000
Incentive Compensation [Line Items]
Common Stock Shares reserved						2,400,000
Shares available for grant						498,714
Stock based compensation expense	2,700,000	2,300,000	5,523,000	7,480,000			2,200,000
Stock option grants- shares			324,565
Restricted stock grants- shares			167,293
Restricted stock grants- fair value			$ 43.38
Performance Cash Compensation Expense			Compensation expense (benefit) recorded related to the performance cash awards during the three months ended September 30, 2012 and 2011 was $3.4 million and $(0.6) million, respectively, and during the six months ended September 30, 2012 and 2011 was $4.1 million and $3.0 million, respectively.
Risk free interest rate			0.76%
Expected life (years)			5
Volatility			50.20%
Dividend yield			1.84%
Weighted average exercise price of options granted	$ 43.38		$ 43.38
Weighted average grant-date fair value of options granted			$ 16.65
Performance cash compensation liability	$ 7,100,000		$ 7,100,000		$ 5,700,000