Income Taxes (Operating Loss Carryforwards) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Internal Revenue Service (IRS) [Member]    
Operating Loss Carryforwards [Line Items]    
Operating loss carryforwards $ 483.1 $ 507.5
State and Local Jurisdiction [Member]    
Operating Loss Carryforwards [Line Items]    
Operating loss carryforwards $ 436.0 $ 449.8