Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Taxes [Line Items]
Effective income tax rate	26.50%	28.10%
Increase/decrease in effective tax rate due to impact of discrete tax items	0.40%	0.80%
Unrecognized tax benefits, increases resulting from current and prior period tax positions	$ 4.8
Total unrecognized tax benefits	20.4
Unrecognized tax payable, current	2.6
Unrecognized tax payable, non-current	$ 17.8