Restructuring - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 26, 2018	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Percent reduction in headcount expected	50.00%
Expected reverse of stock-based compensation from awards forfeited		$ 3,800
Restructuring and related cost, incurred cost		17,807
Assets held-for-sale		1,324	$ 0
One-time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring expense		8,600
Exit Or Disposal Costs
Restructuring Cost and Reserve [Line Items]
Restructuring expense		1,800
Impairment of equipment
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, incurred cost		3,608
Laboratory equipment
Restructuring Cost and Reserve [Line Items]
Assets held-for-sale		$ 1,300