Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended									12 Months Ended
	Mar. 31, 2018	Jan. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Policies
Net (loss) income				$ (45,502)	$ (27,119)	$ (27,732)	$ (35,961)	$ (37,907)	$ (26,017)	$ (23,156)	$ (8,685)	$ (136,314)	$ (95,765)	$ (70,275)
Accumulated deficit				482,162				345,848				482,162	345,848
Cash and cash equivalents				12,620				15,256				12,620	15,256	28,947	$ 87,176
Marketable securities				106,247				130,860				106,247	130,860
Short-term Credit Line, outstanding balance				50,112				49,624				50,112	49,624
Long-term Term Loan, carrying amount				73,065								73,065
Revenues				53,765	$ 56,656	$ 53,617	$ 46,901	49,299	$ 53,889	$ 51,984	$ 61,902	210,939	217,074	190,355
Licensing revenue												$ 5,450	3,106	$ 2,187
Agreement term												4 years
Restricted cash
Restricted cash, long term portion				$ 342				$ 342				$ 342	$ 342
Forecast | Qiagen
Policies
Revenues			$ 40,000
Subsequent Event
Policies
Agreement term		2 years
Subsequent Event | Qiagen
Policies
Potential milestone payments	$ 10,000
Agreement term	10 years