Accrued expenses and other current liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued expenses	$ 33,810	$ 30,690
Derivative instruments	1,368	1,430
Client liability account	2,783	4,005
Other current liabilities	9,709	7,139
Accrued expenses and other current liabilities	$ 47,670	$ 43,264