Goodwill and Intangible assets - Estimated Amortization Expense of Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
2015 (remaining six months)	$ 426		$ 426
2016	846		846
2017	842		842
2018	829		829
2019	709		709
2020	646		646
Thereafter	1,337		1,337
Total	5,635		5,635		$ 1,582
Amortization expense	$ 150	$ 42	$ 211	$ 81