Revenue - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Allowance for doubtful accounts	$ 4,200		$ 4,200		$ 2,000
Prior period sales	$ 656	$ 125	$ 353	$ (300)