- Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 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
Contract asset balance	$ 0	$ 0
Decrease to opening retained earnings	$ 262,833,000		$ 241,972,000
Cumulative impact of adopting Topic 606 | Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Decrease to opening retained earnings		$ 49,000
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Payment terms	30 days
Estimated useful life of assets	1 year
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Payment terms	60 days
Estimated useful life of assets	7 years