Intangible Assets Other Than Goodwill - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	$ 4.8	$ 4.2	$ 8.4	$ 6.6
4.50% Convertible senior notes (due 2014)
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Debt issuance cost written off amount	$ 0.6		$ 0.6