Goodwill and Intangible assets - Estimated Amortization Expense of Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 1,000	$ 200	$ 1,900	$ 500
2017 (remaining six months)	2,031		2,031
2018	4,051		4,051
2019	3,928		3,928
2020	2,460		2,460
2021	2,325		2,325
2022	726		726
Thereafter	1,752		1,752
Total	$ 17,273		$ 17,273		$ 13,273