Consolidated Statements of Changes in Equity and Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Balance at January 1	$ (21,812)
Changes During Year	(6,626)	[1]	(2,343)	[1]	4,730	[1]
Balance at December 31	(28,438)		(21,812)
Postretirement Liability Adjustment [Member]
Balance at January 1	(15,928)	[1]	(12,626)	[1]	(13,834)	[1]
Changes During Year	(5,667)	[1]	(3,302)	[1]	1,208	[1]
Balance at December 31	(21,595)	[1]	(15,928)	[1]	(12,626)	[1]
Unrealized Gain (Loss) on Derivatives-Other [Member]
Balance at January 1	(2,082)	[1]	(2,331)	[1]	(3,289)	[1]
Changes During Year	(788)	[1]	249	[1]	958	[1]
Balance at December 31	(2,870)	[1]	(2,082)	[1]	(2,331)	[1]
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Balance at January 1	154	[1]	(185)	[1]	(718)	[1]
Changes During Year	(360)	[1]	339	[1]	533	[1]
Balance at December 31	(206)	[1]	154	[1]	(185)	[1]
Other Comprehensive Income (Loss) of Affiliated Companies [Member]
Balance at January 1	(3,956)	[1]	(4,327)	[1]	(6,358)	[1]
Changes During Year	189	[1]	371	[1]	2,031	[1]
Balance at December 31	(3,767)	[1]	(3,956)	[1]	(4,327)	[1]
Accumulated Other Comprehensive Loss
Balance at January 1	(21,812)	[1]	(19,469)	[1]	(24,199)	[1]
Changes During Year	(6,626)	[1]	(2,343)	[1]	4,730	[1]
Balance at December 31	$ (28,438)	[1]	$ (21,812)	[1]	$ (19,469)	[1]

[1] Determined using a combined statutory tax rate of 41%.