Long-term Debt (Tables)

6 Months Ended

Jun. 30, 2016

Debt Disclosure [Abstract]

Summary of Long-term Debt

The following table provides a summary of the Company's Notes and the fair values based on quoted market prices in less active markets as of June 30, 2016 and December 31, 2015:

						Level 2 Fair Value as of
	Principal Amount at Par		Issuance Date	Maturity	Interest Due Dates	June 30, 2016		December 31, 2015
	(in millions)					(in millions)
5.50% Senior Notes	$	700.0	February 2015	2022	April 15 and October 15	$	729.8	$	717.5
5.875% Senior Notes	800.0		February 2015	2025	April 15 and October 15	839.0		820.0
5.750% Senior Notes	400.0		February 2014	2024	March 1 and September 1	417.0		411.0
5.375% Senior Notes	500.0		February 2013	2021	February 1 and August 1	531.0		525.0