Fair Value Measurements (Details) (Quoted Prices in Active Markets for Identical Assets (Level 1) [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
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	$ 10.6	[1]	$ 8.4	[1]

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