Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Liability for uncertain tax positions	$ 2.1	$ 3.8
Reversal of liability for uncertain tax positions	$ 2.2
Minimum
Income Taxes [Line Items]
Effective tax rate	29.40%
Maximum
Income Taxes [Line Items]
Effective tax rate	37.10%