Total Interest Expense Under Long Term Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Debt Disclosure [Line Items]
Accretion of debt discount	$ 4,280	$ 2,852	$ 8,410	$ 4,505
Amortization of debt issue costs	217	114	430	287
Accrued interest	2,740	2,634	5,476	5,365
Total Interest Expense	7,237	5,600	14,316	10,157
Non Cash
Debt Disclosure [Line Items]
Non-cash interest expense	$ 4,497	$ 2,966	$ 8,840	$ 4,792