Principal Amount Outstanding under Loan Arrangement (Detail) (USD $) In Thousands, unless otherwise specified				12 Months Ended
	Dec. 31, 2012	Oct. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 June 27, 2012	Dec. 31, 2012 October 18, 2012
Related Party Transaction [Line Items]
Principal amount outstanding at December 31, 2011	$ 119,635		$ 277,203
Borrowings	12,750	125,400	45,000
Capitalization of accrued and unpaid interest due and payable	2,200		5,900	11,876	2,343
Reduction of principal indebtedness related to the issuance of common stock pursuant to common stock purchase agreement completed				(77,187)	(107,350)
Principal amount outstanding at December 31, 2012	$ 119,635		$ 277,203