Components of Interest Expense Attributable to Convertible Notes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Debt Disclosure [Line Items]
Accretion on original issue discount	$ 333	$ 2,205
Amortization of debt issuance costs	682	1,067
4.50% Convertible Notes due 2012
Debt Disclosure [Line Items]
Contractual interest expense	55	2,588
Accretion on original issue discount	45	1,947
Amortization of debt issuance costs	7	334
Interest Expense, Debt, Total	$ 107	$ 4,869