Income taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Tax Credit Carryforward [Line Items]
Net deferred tax assets	$ 3,593
Net deferred tax liabilities		$ 12,685
Net decrease in valuation allowance	300	4,400
Deferred tax assets relating to NOL carryforwards	6,428	4,260
Anticipated refunds received from previously-filed carryback claims		2,800
Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Net deferred tax assets	3,800
Net deferred tax liabilities		12,000
Foreign Tax Authority
Tax Credit Carryforward [Line Items]
Net deferred tax liabilities	300	700
Federal net operating loss, valuation allowances released			$ 6,600
Foreign tax credits carry forwards, deferred tax asset valuation allowances released		$ 5,000
Tax credit carry forwards	$ 20,200