Segments (Details) Revenue by Geography - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 82,640	$ 78,164	$ 73,392	$ 69,760	$ 66,545	$ 63,118	$ 58,275	$ 54,729	$ 303,956	$ 242,667	$ 188,230
UNITED STATES
Segment Reporting Information [Line Items]
Revenues									246,280	195,297	151,361
CANADA
Segment Reporting Information [Line Items]
Revenues									$ 57,676	$ 47,370	$ 36,869