Components of Interest Expense Attributable to Convertible Notes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Debt Disclosure [Line Items]
Accretion on original issue discount	$ 341	$ 583	$ 674	$ 2,788
Amortization of debt issuance costs	694	895	1,376	1,962
4.50% Convertible Notes due 2012
Debt Disclosure [Line Items]
Contractual interest expense	56	421	111	3,009
Accretion on original issue discount	46	318	91	2,265
Amortization of debt issuance costs	7	55	14	389
Interest Expense, Debt, Total	$ 109	$ 794	$ 216	$ 5,663