The Company and Subsequent Events - Summary of Reconciliation of Beginning and Ending Restructuring Liability (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Restructuring Cost And Reserve [Line Items]
Balance, beginning of period
Additions, charged to costs	$ 6,215	$ 7,080
Payments and impairments		(5,143)
Balance, end of period	1,937	1,937
One-Time Employee Termination Benefit Costs
Restructuring Cost And Reserve [Line Items]
Balance, beginning of period
Additions, charged to costs		2,828
Payments and impairments		(1,951)
Balance, end of period	877	877
Contract Termination Costs
Restructuring Cost And Reserve [Line Items]
Balance, beginning of period
Additions, charged to costs		446
Payments and impairments		(18)
Balance, end of period	428	428
Consulting Costs
Restructuring Cost And Reserve [Line Items]
Balance, beginning of period
Additions, charged to costs		1,499
Payments and impairments		(867)
Balance, end of period	$ 632	632
Asset Disposal Costs
Restructuring Cost And Reserve [Line Items]
Additions, charged to costs		2,307
Payments and impairments		$ (2,307)