Components of Interest Expense Attributable to Convertible Notes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Debt Disclosure [Line Items]
Accretion on original issue discount	$ 351	$ 315	$ 1,025	$ 3,103
Amortization of debt issuance costs	706	747	2,082	2,709
4.50% Convertible Notes due 2012
Debt Disclosure [Line Items]
Contractual interest expense	55	55	166	3,064
Accretion on original issue discount	47	43	138	2,308
Amortization of debt issuance costs	8	7	22	396
Interest Expense, Debt, Total	$ 110	$ 105	$ 326	$ 5,768