Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income Tax [Line Items]
Income tax examination, increase (decrease) in liability from prior year	$ 10.9
Reduction in income tax provision, research credit		3.7
Unrecognized tax benefits related to federal, state and foreign taxes	31.5		58.0
Unrecognized tax benefits that would impact effective tax rate	26.0
Accrued interest	3.2		6.6
Decrease in unrecognized tax benefits within the next 12 months	$ 3.7
Number of months unrecognized tax benefits may decrease	12 months