Retirement Benefits (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Pensions
Net Periodic Pension Benefit Cost:
Service cost	$ 1,628,000	$ 1,393,000	$ 5,830,000	$ 5,007,000
Interest cost	2,551,000	2,591,000	10,366,000	10,156,000
Expected return on plan assets	(3,076,000)	(2,680,000)	(11,534,000)	(10,044,000)
Amortization of prior service cost	133,000	133,000	532,000	531,000
Amortization of net actuarial loss	1,950,000	1,353,000	6,091,000	4,315,000
Net periodic benefit cost	3,186,000	2,790,000	11,285,000	9,965,000
Employer contribution	5,100,000
Defined Benefit Plan Estimated Employer Contributions in Current Fiscal Year	6,000,000
SERP
Net Periodic Pension Benefit Cost:
Service cost	7,000	20,000	81,000	73,000
Interest cost	56,000	41,000	198,000	155,000
Amortization of prior service cost	(2,000)	(2,000)	(8,000)	(8,000)
Amortization of net actuarial loss	76,000	33,000	213,000	98,000
Net periodic benefit cost	137,000	92,000	484,000	318,000
OPEB
Net Periodic Pension Benefit Cost:
Service cost	565,000	626,000	2,205,000	2,254,000
Interest cost	1,032,000	1,130,000	4,286,000	4,396,000
Expected return on plan assets	(1,041,000)	(1,050,000)	(4,148,000)	(3,927,000)
Amortization of prior service cost	(253,000)	(253,000)	(1,011,000)	(1,011,000)
Amortization of net actuarial loss	468,000	500,000	1,729,000	1,655,000
Net periodic benefit cost	$ 771,000	$ 953,000	$ 3,061,000	$ 3,367,000