Total Interest Expense Under Long Term Debt Obligations (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 of debt discount	$ 3,818	$ 523	$ 8,323	$ 4,109
Amortization of debt issue costs	274	129	561	449
Coupon interest	2,713	2,883	8,078	7,284
Total Interest Expense	6,805	3,535	16,962	11,842
Non Cash
Debt Disclosure [Line Items]
Non-cash interest expense	$ 4,092	$ 652	$ 8,884	$ 4,558