Accounts Receivable Financing - Additional Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Accounts Notes And Loans Receivable [Line Items]
Amount of total outstanding accounts receivable under a financing arrangement	$ 64.6	$ 32.0
Amount due from the financing company	35.7		28.5
Fees incurred pursuant to the factoring agreement	0.9	0.5
Transfer Of Financial Assets Under Financing Arrangement
Accounts Notes And Loans Receivable [Line Items]
Amount of total outstanding accounts receivable under a financing arrangement	39.2	31.1
Amount due from the financing company	$ 21.3		$ 20.2