Fair Value Measurements (Narrative) (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015		Jun. 30, 2015		Dec. 31, 2014		Nov. 06, 2014	Jun. 26, 2014	Oct. 18, 2013
Cash payment for purchase of royalty right							$ 65,600,000
Royalty rights	$ 280,731,000	[1]	$ 280,731,000	[1]	$ 259,244,000	[2]
Period over which revenue is expected for valuation (in years)			15 years
Transfers from level 1 to level 2, amount	0		$ 0		0
Transfers from level 2 to level 1, amount	$ 0		$ 0		0
Percentage of royalty acquired							75.00%
Depomed [Member]
Cash payment for purchase of royalty right									$ 240,500,000
Purchase of royalty rights									241,300,000
Royalty right purchase transaction costs									$ 800,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	21.00%		21.00%
Fair Value Measurements, Sensitivity Analysis, Description			Should these discount rates increase or decrease by 5%, the fair value of the asset could decrease by $18.4 million or increase by $23.4 million, respectively. A third-party expert was engaged to help management develop its original estimate of the expected future cash flows. The fair value of the asset is subject to variation should those cash flows vary significantly from those estimates. Should the expected royalties increase or decrease by 10%, the fair value of the asset could increase by $15.6 million or decrease by $16.3 million, respectively.
Royalty rights	$ 194,000,000		$ 194,000,000		176,200,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 194,000,000		$ 194,000,000
VB [Member]
Purchase of royalty rights								$ 15,500,000
Fair value inputs, discount rate (in Percent)	17.50%
Fair Value Measurements, Sensitivity Analysis, Description			Should this discount rate increase or decrease by 2.5%, the fair value of this asset could decrease by $1.3 million or increase by $1.5 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase by $0.4 million or decrease by $0.4 million, respectively.
Royalty rights	$ 16,700,000		$ 16,700,000		16,100,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 16,700,000		$ 16,700,000
University of Michigan [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	12.80%		12.80%
Fair Value Measurements, Sensitivity Analysis, Description	Should this discount rate increase or decrease by 2.5%, the fair value of this asset could decrease by $6.1 million or increase by $7.0 million, respectively. Should the expected royalties increase or decrease by 5%, the fair value of the asset could increase by $3.5 million or decrease by $3.5 million, respectively.
Royalty rights	$ 70,100,000		$ 70,100,000		$ 66,900,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 70,100,000		$ 70,100,000

[1] unaudited

[2] Note 1