Income taxes - Summary of Components of Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current deferred income tax assets:
Financing costs	$ 105	$ 92
Non-current deferred income tax assets:
Loss carry-forwards	21,130
Other timing differences	390	386
Valuation allowance	(20,480)
Non-current deferred income tax assets	1,040	386
Non-current deferred income tax liabilities:
Property and equipment	(1,305)	(1,481)
Financing costs	(5)	(80)
Deferred Tax Liabilities, Gross, Total	(1,310)	(1,561)
Non-current deferred income tax, net	$ (270)	$ (1,175)