Summary of Preferred Stock (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Series B Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Convertible preferred stock, cumulative dividend rate	10.00%	10.00%
Series C Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Convertible preferred stock, cumulative dividend rate	10.00%	10.00%
Series D Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Convertible preferred stock, cumulative dividend rate	10.00%	10.00%
Series E Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Convertible preferred stock, cumulative dividend rate	10.00%	10.00%