Organization and Summary of Significant Accounting Policies - Impact of Adoption of ASC on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
ASSETS
Property and equipment, net	$ 29,926		$ 78,723
Operating lease right-of-use assets	77,289		0
Prepaid rent			0
Liabilities:
Operating lease liabilities - current	3,214	$ 1,408	0
Deferred rent			271
Operating lease liabilities - long-term	41,192		0
Accumulated deficit	$ (656,985)		(562,696)
Topic 842
ASSETS
Property and equipment, net		16,223
Operating lease right-of-use assets		8,753
Prepaid rent		36,025
Liabilities:
Operating lease liabilities - current		1,408
Deferred rent		0
Operating lease liabilities - long-term		7,933
Accumulated deficit		(561,799)
Topic 842 | Adjustments Due to the Adoption of ASC Topic 842
ASSETS
Property and equipment, net		(62,500)
Operating lease right-of-use assets		8,753
Prepaid rent		36,025
Liabilities:
Deferred rent		(271)
Operating lease liabilities - long-term		7,933
Accumulated deficit		897
Build-to-Suit Leases
Liabilities:
Operating lease liabilities - long-term			$ 27,689
Build-to-Suit Leases | Topic 842
Liabilities:
Operating lease liabilities - long-term		0
Build-to-Suit Leases | Topic 842 | Adjustments Due to the Adoption of ASC Topic 842
Liabilities:
Operating lease liabilities - long-term		$ (27,689)