RETIREMENT AND OTHER EMPLOYEE BENEFITS(Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Net Periodic Pension Benefit Cost:
Service cost	$ 1,883,000	$ 1,627,000	$ 6,722,000	$ 7,213,000
Interest cost	2,503,000	2,733,000	10,589,000	10,287,000
Expected return on plan assets	(3,390,000)	(3,322,000)	(13,173,000)	(12,625,000)
Amortization of prior service cost	(157,000)	105,000	156,000	503,000
Amortization of net actuarial loss	2,345,000	1,649,000	7,308,000	9,504,000
Net periodic benefit cost	3,184,000	2,792,000	11,602,000	14,882,000
Pension contributions	12,800,000
SERP
Net Periodic Pension Benefit Cost:
Service cost	43,000	29,000	167,000	148,000
Interest cost	92,000	87,000	393,000	338,000
Amortization of prior service cost	(11,000)	(2,000)	(17,000)	(8,000)
Amortization of net actuarial loss	140,000	105,000	539,000	569,000
Net periodic benefit cost	264,000	219,000	1,082,000	1,047,000
OPEB
Net Periodic Pension Benefit Cost:
Service cost	920,000	607,000	2,914,000	2,792,000
Interest cost	1,164,000	1,080,000	4,442,000	3,916,000
Expected return on plan assets	(1,312,000)	(1,196,000)	(4,916,000)	(4,451,000)
Amortization of prior service cost	(253,000)	(253,000)	(1,011,000)	(1,011,000)
Amortization of net actuarial loss	681,000	228,000	1,420,000	1,841,000
Net periodic benefit cost	1,200,000	466,000	2,849,000	3,087,000
Pension contributions	$ 5,000,000
Healthcare benefits
Net Periodic Pension Benefit Cost:
Eligible age	55 years
Minimum service period for eligibility	5 years