Commitments and contingencies - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2012
Commitment And Contingencies [Line Items]
Registration Rights Agreement filing description	The Registration Rights Agreement provided that if a registration statement covering those initial shares was not filed with the SEC on or prior to the date which was five business days after the date which was two business days after the Company’s stockholders approved the Migratory Merger and the Reverse Split or if (1) a registration statement covering those additional shares was not declared effective by the SEC prior to the earlier of (A) five business days after the SEC informed the Company that no review of such registration statement would be made or that the SEC had no further comments on such registration statement, or (B) the 120th day after the deadline for the Company’s filing of that registration statement, or (2) after such registration statement has been declared effective by the SEC, sales cannot be made pursuant to such registration statement for any reason, but excluding any period for which the use of any prospectus included in a registration statement has been suspended if and so long as certain conditions exist (which period may not be for more than 20 consecutive days or for a total of more than 45 days in any 12-month period), then the Company is required to pay amounts representing liquidated damages to each of the investors, on the same basis as the liquidated damages the Company could have been required to pay in connection with the initial registration statement. A registration statement covering the remaining Registrable Securities was declared effective on September 13, 2011 by the SEC, which resolved the contingency regarding the registration statement being declared effective.
Number of business days for filing of registration statement	5 days
Number of business days after stockholders approval for Merger and Reverse Split	2 days
Number of business days after SEC intimation regarding non declaration of additional shares	5 days
Number of days after deadline for filing	120 days
Number of consecutive days for suspension of registration statement	20 days
Aggregated number of days, in which conditions regarding suspension persist	45 days
Number of months as base period for aggregate and consecutive period	12 months