Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Liabilities [Abstract]
Senior notes, fair value	$ 398.9
Recurring [Member]
Liabilities [Abstract]
Interest rate swap	3.7	4.3
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Liabilities [Abstract]
Interest rate swap	0	0
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Liabilities [Abstract]
Interest rate swap	3.7	4.3
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Liabilities [Abstract]
Interest rate swap	$ 0	$ 0