Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Fair Value of Derivataives Table

		Level 1		Level 2		Level 3		Total
Assets:
Current derivative asset	$	-	$	230,385	$	-	$	230,385

Fair Value of Long-Term Debt

		December 31, 2011				December 31, 2010
		Carrying		Estimated		Carrying		Estimated
		Amount		Fair Value		Amount		Fair Value
Long-Term Debt:
5.45% Notes due 2015, issued 2008	$	100,000	$	111,475	$	100,000	$	108,572
7.31% Notes due 2016, issued 2009		62,000		74,817		62,000		72,153
4.98% Notes due 2017, issued 2010		116,000		128,570		116,000		119,385
5.92% Notes due 2018, issued 2008		200,000		231,091		200,000		212,660
7.77% Notes due 2019, issued 2009		173,000		219,552		173,000		203,051
5.50% Notes due 2020, issued 2010		207,000		229,423		207,000		206,233
4.51% Notes due 2020, issued 2010		315,000		318,925		315,000		284,207
5.60% Notes due 2022, issued 2010		87,000		94,165		87,000		84,818
4.66% Notes due 2022, issued 2010		35,000		34,631		35,000		30,989
5.85% Notes due 2025, issued 2010		90,000		99,022		90,000		87,211
4.91% Notes due 2025, issued 2010		175,000		173,835		175,000		152,064
Credit Facility		343,000		343,000		-		-
	$	1,903,000	$	2,058,506	$	1,560,000	$	1,561,343