New Revenue Recognition Standard - Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Current assets:
Accounts receivable, net	$ 29,873		$ 32,260
Total current assets	250,688		277,746
Total assets	390,886		487,439
Current liabilities:
Deferred revenue	0		3,872
Total current liabilities	86,474		109,749
Deferred revenue, less current portion	0
Total liabilities	107,624		136,100
Stockholders’ equity:
Accumulated deficit	(599,886)		(502,107)
Total stockholders’ equity	283,262		351,339
Total liabilities and stockholders’ equity	390,886		$ 487,439
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Current assets:
Accounts receivable, net	127
Total current assets	127
Total assets	127
Current liabilities:
Deferred revenue	2,963
Total current liabilities	2,963
Deferred revenue, less current portion	251
Total liabilities	3,214
Stockholders’ equity:
Accumulated deficit	(3,087)	$ 4,700
Total stockholders’ equity	(3,087)
Total liabilities and stockholders’ equity	127
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Current assets:
Accounts receivable, net	30,000
Total current assets	250,815
Total assets	391,013
Current liabilities:
Deferred revenue	2,963
Total current liabilities	89,437
Deferred revenue, less current portion	251
Total liabilities	110,838
Stockholders’ equity:
Accumulated deficit	(602,973)
Total stockholders’ equity	280,175
Total liabilities and stockholders’ equity	$ 391,013