Accounts payable and accrued obligations - Schedule of Accounts Payable and Other Accrued Obligations (Detail) (As Restated [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
As Restated [Member]
Schedule Of Accrued Liabilities [Line Items]
Trade payables	$ 29,056	$ 30,814
Allowance for rebates	20,683	11,023
Accrued product royalty	9,292	12,275
Allowance for returns	2,650	5,056
Accrued data and distribution fees	4,459	8,449
Accrued GPO administrative fees	2,672	2,650
Inventory management fee	1,690	3,050
Accrued income taxes	2,259	2,522
Allowance for chargebacks	9,372	15,153
Other accrued obligations	1,459	2,819
Total accounts payable and other accrued obligations	$ 83,592	$ 93,811