Employee Benefit Plans (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 13,039	$ 12,312	$ 16,534
Interest cost	97,293	95,453	93,493
Expected return on plan assets	(124,150)	(114,166)	(113,370)
Amortization of prior service credit	(6,970)	(6,979)	(7,010)
Amortization of actuarial loss	53,039	35,264	21,990
Curtailment gain			(4,298)
Net periodic benefit cost	32,251	21,884	7,339
Other Changes in plan assets and benefit obligations recognized in other comprehensive income
Current year actuarial loss (gain)	311,038	60,777	(125,816)
Recognition of actuarial loss	(53,039)	(35,264)	(21,990)
Current year prior service cost (credit)		1,148
Recognition of prior service cost	6,970	6,979	11,308
Total recognized in other comprehensive income	264,969	33,640	(136,498)
Total recognized in net periodic benefit cost and other comprehensive income	297,220	55,524	(129,159)
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost
Service cost			443
Interest cost	474	605	1,264
Amortization of prior service credit	(930)	(1,059)	(225)
Amortization of actuarial loss	1,708	1,759	1,759
Net periodic benefit cost	1,252	1,305	3,241
Other Changes in plan assets and benefit obligations recognized in other comprehensive income
Current year actuarial loss (gain)	(3,911)	340	(1,190)
Recognition of actuarial loss	(1,708)	(1,759)	(1,759)
Current year prior service cost (credit)	362		(13,182)
Recognition of prior service cost	930	1,059	225
Total recognized in other comprehensive income	(4,327)	(360)	(15,906)
Total recognized in net periodic benefit cost and other comprehensive income	$ (3,075)	$ 945	$ (12,665)