Debt (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Debt Outstanding

	December 31,
	2014			2013
	(in millions)
Revolving Credit Facility due 2019	$	—		$	480.0
Term Loan due 2017	—			300.0
6.05% Senior Notes due 2016	176.8			176.8
6.80% Senior Notes due 2018	134.0			134.0
6.80% Senior Notes due 2020	136.0			136.0
6.875% Senior Notes due 2021	625.0			625.0
5.375% Senior Notes due 2022	500.0			500.0
5.25% Senior Notes due 2023	650.0			650.0
Total principal amount of debt	2,221.8			3,001.8
Less unamortized discount	(3.7		)	(4.3		)
Total long-term debt outstanding	$	2,218.1		$	2,997.5