Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Income Taxes [Line Items]
Effective income tax rate	27.10%	29.60%
Increase/decrease in effective tax rate due to impact of discrete tax items	0.70%	0.40%
Unrecognized tax benefits, increases resulting from current and prior period tax positions	$ 0.1
Total unrecognized tax benefits	20.5
Unrecognized tax payable, current	2.3
Unrecognized tax payable, non-current	$ 18.2