Taxation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Income Taxes [Line Items]
Effective tax rate	20.90%	16.70%	21.40%	12.60%
Unrecognized tax benefit	$ 5.8		$ 5.8		$ 5.6
Description of income tax examination			The Company's operating subsidiaries in specific countries may be subject to audit by various tax authorities and may have different statutes of limitations expiration dates. With limited exceptions, the Company's major subsidiaries that operate in the United States, United Kingdom and Australia are no longer subject to tax examinations for years before 2005, 2008 and 2005, respectively.
Domestic [Member]
Income Taxes [Line Items]
Effective tax rate			0.00%