Financing (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Outstanding financing facilities

	December 31,
	2017		2016
Revolving Credit Facility, weighted-average variable interest rate of 2.675%	$	346,000	$	—
$500 million, 4.875% Senior Notes due 2021(1), effective interest rate of 4.956%	497,565		496,758
$300 million, 4.625% Senior Notes due 2021(2), effective interest rate of 4.645%	298,961		298,679
$300 million, 3.800% Senior Notes due 2022(3), effective interest rate of 3.845%	298,214		297,868
$300 million, 3.850% Senior Notes due 2023(4), effective interest rate of 3.851%	298,583		298,355
$500 million, 3.550% Senior Notes due 2026(5), effective interest rate of 3.570%	495,792		495,359
$750 million, 3.600% Senior Notes due 2027(6), effective interest rate of 3.619%	743,275		—
Long-term debt	$	2,978,390	$	1,887,019

⁽¹⁾  Net of unamortized discount of $1.1 million and $1.4 million as of December 31, 2017 and 2016, respectively, and debt issuance costs of $1.4 million and $1.8 million as of December 31, 2017 and 2016, respectively.

⁽²⁾  Net of unamortized discount of $0.2 million and $0.2 million as of December 31, 2017 and 2016, respectively, and debt issuance costs of $0.8 million and $1.1 million as of December 31, 2017 and 2016, respectively.

⁽³⁾  Net of unamortized discount of $0.6 million and $0.7 million as of December 31, 2017 and 2016, respectively, and debt issuance costs of $1.2 million and $1.5 million as of December 31, 2017 and 2016, respectively.

⁽⁴⁾  Net of unamortized discount of less than $0.1 million as of December 31, 2017 and 2016, and debt issuance costs of $1.4 million and $1.6 million as of December 31, 2017 and 2016, respectively.

⁽⁵⁾  Net of unamortized discount of $0.7 million and $0.8 million as of December 31, 2017 and 2016, respectively, and debt issuance costs of $3.5 million and $3.9 million as of December 31, 2017 and 2016, respectively.

⁽⁶⁾  Net of unamortized discount of $1.2 million as of December 31, 2017, and debt issuance costs of $5.6 million as of December 31, 2017.

Principle maturities of financing facilities

	Scheduled Maturities
2018	$	—
2019	—
2020	—
2021	800,000
2022	646,000
Thereafter	1,550,000
Total	$	2,996,000