Income taxes - Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
U.S. net operating loss carryforwards	$ 62,844	$ 33,767
Foreign net operating loss carryforwards	194	899
Tax credit carryforwards	47,386	23,274
Capitalized research and development expenses, net	979	1,372
Capital lease	24,315
Deferred revenue	16,438	12,050
Capitalized license fees	5,488	384
Accruals and other	19,486	7,168
Total deferred tax assets	177,130	78,914
Intangible assets	(9,606)	(11,084)
Fixed assets	(26,681)	(2,526)
Less valuation allowance	$ (140,843)	$ (65,304)