Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Changes in benefit obligation
Benefit obligation at beginning of year	$ 1,689,011,000	$ 1,502,084,000
Service cost	13,039,000	12,312,000	16,534,000
Interest cost	97,293,000	95,453,000	93,493,000
Plan participants' contributions	3,887,000	3,672,000
Plan amendments		1,148,000
Actuarial loss (gain)	219,804,000	122,050,000
Exchange rate changes	(4,656,000)	7,082,000
Gross benefits paid	(59,979,000)	(54,790,000)
Benefit obligation at end of year	1,958,399,000	1,689,011,000	1,502,084,000
Assumptions used to measure pension and other postretirement benefit obligations for plans
Weighted-average discount rate	5.17%	5.74%
Rate of increase in future compensation levels	3.30%	3.39%
Other Postretirement Benefits [Member]
Changes in benefit obligation
Benefit obligation at beginning of year	12,329,000	13,511,000
Service cost			443,000
Interest cost	474,000	605,000	1,264,000
Plan participants' contributions	3,412,000	3,787,000
Plan amendments	362,000
Actuarial loss (gain)	(3,911,000)	340,000
Gross benefits paid	(5,326,000)	(6,255,000)
Less Federal subsidy	174,000	341,000
Benefit obligation at end of year	$ 7,514,000	$ 12,329,000	$ 13,511,000
Assumptions used to measure pension and other postretirement benefit obligations for plans
Weighted-average discount rate	4.00%	4.25%
Rate of increase in future compensation levels	0.00%	0.00%