EMPLOYEE BENEFIT PLANS (Details) $ / shares in Units, $ in Thousands, £ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 GBP (£)	Mar. 31, 2015 USD ($) $ / shares
Pension Plan [Line Items]
Service cost	$ 2,399	$ 2,087	$ 4,772	$ 4,333
Interest cost	5,226	6,437	10,396	13,366
Expected return on assets	(7,014)	(7,638)	(13,955)	(15,861)
Amortization of unrecognized losses	2,153	1,641	4,285	3,409
Net periodic pension cost	$ 2,764	2,527	$ 5,498	5,247
Incentive Compensation [Line Items]
Common Stock, par value | $ / shares	$ 0.01		$ 0.01				$ 0.01
Stock based compensation expense	$ 6,400	4,200	$ 10,380	8,407
Stock option grants- shares | shares	26,406		740,718
Restricted stock grants- shares | shares	22,910		213,349
Restricted stock grants- fair value | $ / shares	$ 45.01		$ 56.76
Risk free interest rate			1.62%
Expected life (years)			6 years
Volatility			28.10%
Dividend yield			3.14%
Weighted average exercise price of options granted | $ / shares			$ 57.52
Weighted average grant-date fair value of options granted | $ / shares			$ 10.71
Performance cash compensation liability	$ 13,600		$ 13,600				$ 21,000
Performance cash compensation expense	$ 1,600	$ 2,500	$ 1,700	$ 4,600
Plan 2007
Incentive Compensation [Line Items]
Common Stock shares reserved | shares	5,400,000		5,400,000
Shares available for grant | shares	1,438,501		1,438,501
Pension Plan | UK Pension Plans
Pension Plan [Line Items]
Cash Contributions			$ 5,000
Pension Plan | UK Pension Plans | Forecast
Pension Plan [Line Items]
Estimated cash contributions					$ 18,100
Pension Plan | Norway pension plan
Pension Plan [Line Items]
Cash Contributions			$ 2,000
Pension Plan | Norway pension plan | Forecast
Pension Plan [Line Items]
Estimated cash contributions					$ 11,700
Pension Plan | UK staff pension plan
Pension Plan [Line Items]
Cash Contributions						£ 12.5	$ 18,600