Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended			3 Months Ended		12 Months Ended
	Nov. 30, 2018 ft²	Jan. 31, 2018 ft²	Mar. 31, 2014 USD ($) ft²	Mar. 31, 2019 ft² Building l	Mar. 31, 2018	Dec. 31, 2018 USD ($)	Dec. 31, 2017 ft²
Commitments and Contingencies [Line Items]
Lease agreement, space | ft²		63,761		45,000
Lease agreement, term			8 years
Lease agreement, commencement date			Aug. 01, 2014
Lease agreement, number buildings leased | Building				4
Lessee, Operating Lease, Option to Extend							five-year options to extend through July 2035
Lessee, Operating Lease, Lease Not yet Commenced, Option to Extend				Excludes approximately $6 million associated with two of the three 5-year renewal options for the Rancho Dominguez original lease since the renewal options have not been executed
Maximum [Member]
Commitments and Contingencies [Line Items]
Bioreactors used in perfusion cell culture applications | l				2,000
Minimum [Member]
Commitments and Contingencies [Line Items]
Bioreactors used in perfusion cell culture applications | l				50
NGL Impact A [Member] | Research and Development Arrangement [Member]
Commitments and Contingencies [Line Items]
Payments to Navigo in connection with this program, which are recorded to research and development expenses | $						$ 2.4
Spectrum Inc.
Commitments and Contingencies [Line Items]
Lease agreement, expiration date				Nov. 30, 2025	Jul. 15, 2035
Lease agreement, space | ft²	15,000						54,000
Before Amendment
Commitments and Contingencies [Line Items]
Lease agreement, space | ft²			56,000
Security deposit | $			$ 0.2
After Amendment
Commitments and Contingencies [Line Items]
Lease agreement, space | ft²			76,000
Security deposit | $			$ 0.5
Expansion Space
Commitments and Contingencies [Line Items]
Lease agreement, space | ft²			19,900
Annual rent expense | $			$ 0.4