Total Interest Expense Under Long Term Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Debt Disclosure [Line Items]
Accretion of debt discount	$ 4,130	$ 1,653
Amortization of debt issue costs	213	173
Coupon interest	2,736	2,731
Total Interest Expense	7,079	4,557
Non Cash
Debt Disclosure [Line Items]
Non-cash interest expense	$ 4,343	$ 1,826