Credit Facilities, Short-term Borrowings and Long-term Debt (Details 1) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Long-term Debt
Total debt excluding short-term borrowings	$ 2,791,073	$ 2,432,762	$ 2,426,480
Less current maturities of long-term debt	5,230	5,246	425,300	[1]
Total long-term debt	2,785,843	2,427,516	2,001,180	[1]
Estimated fair value of total long-term debt	2,857,684	2,559,059	2,240,447
6.50% 5.5-year notes issued 2011 [Member]
Long-term Debt
Total debt excluding short-term borrowings	500,000	0	0
7.50% 10-year notes issued 2011 [Member]
Long-term Debt
Total debt excluding short-term borrowings	600,000	0	0
5-year floating-rate term loan issued 2010 [Member]
Long-term Debt
Total debt excluding short-term borrowings	0	450,000	0
10.125% 7-year notes issued 2009 [Member]
Long-term Debt
Total debt excluding short-term borrowings	149,628	149,597	149,567
10.375% 10-year notes issued 2009 [Member]
Long-term Debt
Total debt excluding short-term borrowings	248,457	248,391	248,329
3-year floating-rate term loan issued 2008 [Member]
Long-term Debt
Total debt excluding short-term borrowings	0	0	100,000
7.00% 10-year notes issued 2008 [Member]
Long-term Debt
Total debt excluding short-term borrowings	399,675	399,658	399,641
3-year floating-rate notes issued 2007 [Member]
Long-term Debt
Total debt excluding short-term borrowings	0	0	325,000
5.60% 5-year notes issued 2007 [Member]
Long-term Debt
Total debt excluding short-term borrowings	134,483	299,773	299,719
6.40% 10-year notes issued 2007 [Member]
Long-term Debt
Total debt excluding short-term borrowings	349,861	349,852	349,844
7.15% 30-year notes issued 2007 [Member]
Long-term Debt
Total debt excluding short-term borrowings	239,717	249,324	249,321
Private placement notes [Member]
Long-term Debt
Total debt excluding short-term borrowings	0	0	15,181
Medium-term notes [Member]
Long-term Debt
Total debt excluding short-term borrowings	21,000	21,000	21,000
Industrial revenue bonds [Member]
Long-term Debt
Total debt excluding short-term borrowings	14,000	14,000	17,550
Other notes [Member]
Long-term Debt
Total debt excluding short-term borrowings	1,349	1,438	1,648
Fair value adjustments [Member]
Long-term Debt
Total debt excluding short-term borrowings	(7,419)	0	0
6.30% 5-year notes issued 2008 [Member]
Long-term Debt
Total debt excluding short-term borrowings	$ 140,322	$ 249,729	$ 249,680

[1] As Restated, See Note 1