Common and Preferred Stock - Additional Information (Detail) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Nov. 16, 2015 shares	Nov. 09, 2015 shares	Feb. 08, 2012 USD ($) $ / shares $ / Right shares	Nov. 01, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($)	Oct. 23, 2015 shares	Sep. 30, 2015 shares	Aug. 14, 2015 USD ($)
Class of Stock [Line Items]
Common stock, shares authorized					550,000,000	550,000,000
Common stock, par value | $ / shares					$ 0.01	$ 0.01
Undesignated preferred stock, shares authorized					10,000,000	10,000,000
Undesignated preferred stock, par value | $ / shares					$ 0.01	$ 0.01
Common stock, shares issued					428,670,943	406,059,089
Common stock, shares outstanding					428,670,943	406,059,089
Common stock shares sold aggregate price | $					$ 27,844		$ 48,888
Issuance costs associated with the Tel Aviv Stock Exchange | $					$ 548		1,103
Percentage of shares of common stock issued for offering	1.15%
Restricted warrants issued to purchase number of common stock for offering	159,303
Exercise price of restricted warrants per share in connection with the offering | $ / shares					$ 2.61
Warrants exercisable period					5 years
Common stock loaned under share lending agreement, shares						9,000,000			9,000,000
Nominal lending fee | $ / shares						$ 0.01
Returned shares of common stock under share lending agreement								9,000,000
Number of Unit Sold in an Underwritten public offering			35,937,500
Warrant to purchase of a share of common stock | $ / Right			0.6
Net proceeds from offering | $			$ 80,600
Proceeds from exercise warrants | $					$ 10,123	$ 27,779	$ 94,147
Warrants expiration, date					Feb. 08, 2016
Warrant Liability
Class of Stock [Line Items]
Exercise price of restricted warrants per share in connection with the offering | $ / shares			$ 2.40
Number of warrants are exercisable			21,562,500
Duration for Expiration of warrants			4 years
Underwriters
Class of Stock [Line Items]
Number of Unit Sold in an Underwritten public offering			4,687,500
Purchased Price of the units by underwriters | $ / Right			2.256
Public
Class of Stock [Line Items]
Purchased Price of the units by underwriters | $ / Right			2.40
Related Party
Class of Stock [Line Items]
Units sold composition description			Each unit consisting of one share of common stock and a warrant to purchase 0.6 of a share of common stock
TEL AVIV STOCK EXCHANGE
Class of Stock [Line Items]
Common stock, shares authorized		50,000,000
Percentage of shares price per share		97.00%
Common stock shares sold				13,852,435
Common stock shares sold aggregate price | $				$ 34,710	$ 34,710
Share price | $ / shares				$ 2.61
Issuance costs associated with the Tel Aviv Stock Exchange | $				$ 1,433	$ 1,432
Senior convertible notes due August 15, 2015
Class of Stock [Line Items]
Principal amount | $						$ 100,000				$ 32,100