Total Interest Expense Under Long Term Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Debt Disclosure [Line Items]
Accretion of debt discount	$ 4,407	$ 3,818	$ 12,817	$ 8,323
Amortization of debt issue costs	221	274	651	561
Accrued interest	2,736	2,713	8,212	8,078
Total Interest Expense	7,364	6,805	21,680	16,962
Non Cash
Debt Disclosure [Line Items]
Non-cash interest expense	$ 4,628	$ 4,092	$ 13,468	$ 8,884