Debt (Tables)

9 Months Ended

Sep. 30, 2014

Debt Disclosure [Abstract]

Schedule of Debt

Long-term debt consisted of the following at September 30, 2014 and December 31, 2013:

	September 30, 2014		December 31, 2013
Senior unsecured notes:
7.375% Senior Notes due March 2014	$	—	$	249,964
3.45% Senior Notes due August 2015		350,000		350,000
3.05% Senior Notes due March 2016		299,978		299,967
2.50% Senior Notes due March 2017		299,912		299,886
7.50% Senior Notes due March 2019		201,695		201,695
4.90% Senior Notes due August 2020		499,118		499,022
4.625% Senior Notes due March 2021		399,614		399,576
3.95% Senior Notes due March 2022		399,242		399,178
6.20% Senior Notes due August 2040		399,894		399,893
6.05% Senior Notes due March 2041		397,672		397,646
5.25% Senior Notes due March 2042		498,303		498,283
Total senior unsecured notes		3,745,428		3,995,110
Commercial paper program		991,653		1,561,141
Total long-term debt	$	4,737,081	$	5,556,251

Estimated Fair Value of Our Long-Term Debt

The following table presents the estimated fair value of our long-term debt as of September 30, 2014 and December 31, 2013, respectively:

	September 30, 2014				December 31, 2013
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Senior unsecured notes:
7.375% Senior Notes due March 2014	$	—	$	—	$	249,964	$	253,634
3.45% Senior Notes due August 2015		350,000		357,087		350,000		363,019
3.05% Senior Notes due March 2016		299,978		306,752		299,967		309,878
2.50% Senior Notes due March 2017		299,912		303,855		299,886		302,891
7.50% Senior Notes due March 2019		201,695		232,264		201,695		232,839
4.90% Senior Notes due August 2020		499,118		530,788		499,022		528,597
4.625% Senior Notes due March 2021		399,614		413,996		399,576		413,868
3.95% Senior Notes due March 2022		399,242		391,616		399,178		390,520
6.20% Senior Notes due August 2040		399,894		416,991		399,893		421,720
6.05% Senior Notes due March 2041		397,672		408,334		397,646		417,312
5.25% Senior Notes due March 2042		498,303		458,360		498,283		476,873
Total senior unsecured notes		3,745,428		3,820,043		3,995,110		4,111,151
Commercial paper program		991,653		991,653		1,561,141		1,561,141
Total long-term debt	$	4,737,081	$	4,811,696	$	5,556,251	$	5,672,292