Fair Value Measurements (Details) (Quoted Prices in Active Markets for Identical Assets (Level 1) [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Investment in marketable equity securities	$ 9.5	[1]	$ 10.6	[1]

[1] Investment in marketable equity securities is recorded in Other assets, net in the accompanying Consolidated Balance Sheets.