Summary of Significant Accounting Policies (Capitalized Software and Hardware) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment
Amortization expense	$ 1.4	$ 1.1	$ 0.8
Prepaid Expenses and Other Current Assets
Property, Plant and Equipment
Capitalized software and hardware	1.2	0.8
Other Assets
Property, Plant and Equipment
Capitalized software and hardware	$ 4.9	$ 2.8
Minimum
Property, Plant and Equipment
Amortization period (in years)	1 year
Maximum
Property, Plant and Equipment
Amortization period (in years)	5 years