Revenue from Contracts with Customers - Summary of Revenue from Contracts with Customers Cumulative Effect (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues		$ 169,424	$ 135,291	$ 480,187	$ 352,645
Accumulated deficit		(1,204,783)		(1,204,783)		$ (1,192,570)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues		5,701		9,586
Cost of royalty revenues	$ (5,955)
Accumulated deficit	26,556	(17,605)		(17,605)
License and Service [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues		19,786	39,444	76,524	82,779
License and Service [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	10,281	7,448		9,407
Royalty [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues		22,662	$ 16,670	58,887	$ 46,025
Royalty [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 22,230	$ (1,747)		$ 179