RETIREMENT PLAN AND POST-RETIREMENT BENEFITS, Plan Obligations, Plan Assets and Funded Status (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Pension Benefits [Member]
Change in Benefit Obligations [Rollforward]
Benefit obligation, January 1	$ 806,034		$ 757,748
Service cost	18,427		18,910		18,837
Interest cost	40,676		42,872		44,145
Plan participants' contributions
Actuarial loss (gain)	18,552		54,890
Benefits paid	42,507		58,002
Plan amendments	577		(10,384)
Special termination benefits	286		0		300
Remeasurement adjustment	0		0
Benefit obligation, December 31	842,045		806,034		757,748
Change in Plan Assets [Rollforward]
Fair value of plan net assets, January 1	729,940		670,794
Actual return on plan assets	78,104		70,838
Employer contributions	41,286		41,698
Plan participants' contributions
Benefits paid	37,850		53,390
Fair value of plan net assets, December 31	811,480		729,940		670,794
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(30,565)	[1]	(76,094)	[1]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	6.75%		6.75%
Other Post-Retirement Benefits [Member]
Change in Benefit Obligations [Rollforward]
Benefit obligation, January 1	163,423		154,287
Service cost	2,611		2,466		2,421
Interest cost	8,360		8,736		10,072
Plan participants' contributions	2,325		1,924
Actuarial loss (gain)	(12,525)		9,166
Benefits paid	12,255		12,495
Plan amendments	0		(661)
Special termination benefits	100		0		2,800
Remeasurement adjustment	0		0
Benefit obligation, December 31	152,039		163,423		154,287
Change in Plan Assets [Rollforward]
Fair value of plan net assets, January 1	93,648		93,298
Actual return on plan assets	8,615		10,627
Employer contributions	863		294
Plan participants' contributions	2,325		1,924
Benefits paid	12,255		12,495
Fair value of plan net assets, December 31	93,196		93,648		93,298
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	$ (58,843)	[1]	$ (69,775)	[1]

[1] Amounts recognized as non-current liabilities (accrued retirement benefits) in the consolidated balance sheets as of December 31, 2011 and 2010.