- Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Instrument warranty term	1 year
Kits and accessories warranty term	60 days
Decrease to opening retained earnings	$ 308,156		$ 241,972
Cumulative impact of adopting Topic 606 | Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Decrease to opening retained earnings		$ 49
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Estimated useful life of assets	1 year
Payment terms	30 days
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Estimated useful life of assets	7 years
Payment terms	60 days