Components of Interest Expense Attributable to Convertible Notes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Disclosure [Line Items]
Accretion on original issue discount	$ 3,427	$ 8,109	$ 7,523
Amortization of debt issuance costs	3,380	3,875	2,679
4.50% Convertible Notes due 2012
Debt Disclosure [Line Items]
Contractual interest expense	3,119	10,350	10,350
Accretion on original issue discount	2,353	7,371	6,782
Amortization of debt issuance costs	403	1,242	1,387
Interest Expense, Debt, Total	$ 5,875	$ 18,963	$ 18,519