Debt (Tables)

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Schedule of Debt

Our debt consisted of the following at December 31, 2015 and 2014:

	December 31,			December 31,
	2015			2014
Senior unsecured notes:
3.45% Senior Notes due 2015	$	—		$	350,000
3.05% Senior Notes due 2016		299,997			299,982
2.50% Senior Notes due 2017		299,956			299,920
4.00% Senior Notes due 2018		249,602			—
7.50% Senior Notes due 2019		201,695			201,695
4.90% Senior Notes due 2020		499,287			499,151
4.625% Senior Notes due 2021		399,680			399,627
3.95% Senior Notes due 2022		399,354			399,264
5.95% Senior Notes due 2025		448,814			—
6.20% Senior Notes due 2040		399,896			399,895
6.05% Senior Notes due 2041		397,719			397,681
5.25% Senior Notes due 2042		498,338			498,310
6.95% Senior Notes due 2045		394,563			—
Total senior unsecured notes		4,488,901			3,745,525
Credit facilities & commercial paper program		—			1,123,495
Total debt		4,488,901			4,869,020
Less: Current maturities of long-term debt		(299,997	)		—
Total long-term debt	$	4,188,904		$	4,869,020

Repayments of Total Debt

Aggregate principal repayments of total debt for the next five years and thereafter are as follows:

2016		2017		2018		2019		2020		Thereafter		Total
$	299,997	$	299,956	$	249,602	$	201,695	$	499,287	$	2,938,364	$	4,488,901

Estimated Fair Value of Our Long-Term Debt

The following table presents the estimated fair value of our total debt as of December 31, 2015 and 2014:

	December 31, 2015				December 31, 2014
	Carrying		Estimated		Carrying		Estimated
	Value		Fair Value		Value		Fair Value
Senior unsecured notes:
3.45% Senior Notes due 2015	$	—	$	—	$	350,000	$	354,992
3.05% Senior Notes due 2016		299,997		299,340		299,982		302,515
2.50% Senior Notes due 2017		299,956		284,334		299,920		287,014
4.00% Senior Notes due 2018		249,602		227,285		—		—
7.50% Senior Notes due 2019		201,695		194,273		201,695		212,068
4.90% Senior Notes due 2020		499,287		378,761		499,151		471,095
4.625% Senior Notes due 2021		399,680		289,450		399,627		363,837
3.95% Senior Notes due 2022		399,354		265,643		399,264		346,425
5.95% Senior Notes due 2025		448,814		308,870		—		—
6.20% Senior Notes due 2040		399,896		237,005		399,895		350,351
6.05% Senior Notes due 2041		397,719		239,464		397,681		343,653
5.25% Senior Notes due 2042		498,338		279,919		498,310		385,181
6.95% Senior Notes due 2045		394,563		255,887		—		—
Total senior unsecured notes		4,488,901		3,260,231		3,745,525		3,417,131
Credit facilities and commercial paper program		—		—		1,123,495		1,123,496
Total debt	$	4,488,901	$	3,260,231	$	4,869,020	$	4,540,627