Acquisitions - Pro forma (unaudited) (Details) - 2018 and 2019 Acquisitions - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Acquisition
Revenue	$ 76,255	$ 60,715	$ 142,961	$ 118,301
Net loss	$ (6,395)	$ (35,803)	$ (18,104)	$ (59,889)
Net loss per share, basic (in dollars per share)	$ (0.31)	$ (1.86)	$ (0.88)	$ (3.13)
Net loss per share, diluted (in dollars per share)	$ (0.31)	$ (1.86)	$ (0.88)	$ (3.13)