Income Taxes - Summary of Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation Of Unrecognized Tax Benefits [Line Items]
Beginning Balance	$ 4.8	$ 4.4	$ 3.6
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	0.5
Increases related to current year tax positions	0.9	0.5	0.8
Decreases due to statute of limitation expiration		(0.1)
Ending Balance	$ 6.2	$ 4.8	$ 4.4