Total Interest Expense Under Long Term Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Debt Disclosure [Line Items]
Accretion of debt discount	$ 2,852	$ 2,152	$ 4,505	$ 3,587
Amortization of debt issue costs	114	192	287	320
Accrued interest	2,634	2,724	5,365	4,400
Total Interest Expense	5,600	5,068	10,157	8,307
Non Cash
Debt Disclosure [Line Items]
Non-cash interest expense	$ 2,966	$ 2,344	$ 4,792	$ 3,907