Build-to-Suit Lease - Additional Information (Detail) $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2017 USD ($) ft² Option	Dec. 31, 2015 ft² Option	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)
Brisbane Build-to-Suit Lease [Member]
Operating Leased Assets [Line Items]
Property leased | ft²	87,700		87,700
Lease expiration date			May 31, 2029
Operating lease expiration period	10 years
Number of lease term extension options | Option	2
Letter of credit	$ 3.5
Costs capitalized			$ 21.2
Brisbane Build-to-Suit Lease [Member] | Building [Member]
Operating Leased Assets [Line Items]
Costs capitalized	$ 20.9		$ 20.9
Brisbane Build-to-Suit Lease [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Lease agreement, extendable lease term	10 years
Point Pinole Build-to-Suit Lease [Member]
Operating Leased Assets [Line Items]
Property leased | ft²		41,400
Lease expiration date			Dec. 31, 2021
Operating lease expiration period		5 years
Number of lease term extension options | Option		2
Costs capitalized				$ 3.9
Point Pinole Build-to-Suit Lease [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Lease agreement, extendable lease term		10 years