Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Measurements Tables [Abstract]

Fair Value of Long-Term Debt

		Level 1		Level 2		Level 3		Total
Assets:
Current derivative asset	$	-	$	104,190	$	-	$	104,190

		December 31, 2014				December 31, 2013
		Carrying		Estimated		Carrying		Estimated
		Amount		Fair Value		Amount		Fair Value
5.45% Notes due March 2015, issued 2008	$	100,000	$	101,931	$	100,000	$	105,913
7.31% Notes due March 2016, issued 2009		62,000		65,027		62,000		70,228
4.98% Notes due January 2017, issued 2010		116,000		116,240		116,000		126,342
5.92% Notes due March 2018, issued 2008		200,000		203,738		200,000		226,127
5.75% Notes due December 2018, issued 2013		450,000		414,505		450,000		466,946
7.77% Notes due March 2019, issued 2009		173,000		187,105		173,000		211,877
5.50% Notes due January 2020, issued 2010		207,000		201,371		207,000		229,068
4.51% Notes due October 2020, issued 2010		315,000		283,335		315,000		323,732
5.60% Notes due January 2022, issued 2010		87,000		82,581		87,000		95,736
4.66% Notes due October 2022, issued 2010		35,000		30,476		35,000		35,494
6.125% Notes due October 2024, issued 2014		850,000		754,485		-		-
5.85% Notes due January 2025, issued 2010		90,000		83,876		90,000		99,142
4.91% Notes due October 2025, issued 2010		175,000		147,649		175,000		175,744
Credit Facility due October 2016		518,000		518,000		460,000		460,000
	$	3,378,000	$	3,190,319	$	2,470,000	$	2,626,349