Debt (Tables)

6 Months Ended

Jun. 30, 2015

Debt Disclosure [Abstract]

Schedule of debt

(in millions)	June 30, 2015		December 31, 2014
5.9% Senior Notes, due 2017 1	$	400	$	400
4.0% Senior Notes, due 2025 2	695		—
6.55% Senior Notes, due 2037 3	399		399
Long-term debt	$	1,494	$	799

1 Interest payments are due semiannually on April 15 and October 15, and, as of June 30, 2015, the unamortized debt discount is less than $1 million.

2 Interest payments are due semiannually on June 15 and December 15, and, as of June 30, 2015, the unamortized debt discount is approximately $5 million.

3 Interest payments are due semiannually on May 15 and November 15, and, as of June 30, 2015, the unamortized debt discount is approximately $1 million.