Customer Concentration (Percentage of Total Revenue From Licenses Over 10% of Revenue) (Detail)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Kaleo [Member] | Interest revenues [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	0.00%	10.00%
Elan [Member] | Tysabri [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	7.00%	31.00%
Depomed [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	19.00%	14.00%
Noden [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	48.00%
Noden [Member] | Tysabri [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage		28.00%
LENSAR [Member] | Interest revenues [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	13.00%	0.00%