Fair Value Measurements (Narrative) (Detail) - USD ($)					1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 21, 2016	Jul. 08, 2016	Jun. 02, 2016	Sep. 22, 2015	Apr. 30, 2013	Sep. 30, 2016		Sep. 30, 2016		Sep. 30, 2015	Jul. 09, 2016	May 09, 2016	Dec. 31, 2015		Sep. 23, 2015	Sep. 18, 2015	Jul. 28, 2015	Nov. 06, 2014	Jun. 26, 2014	Oct. 18, 2013	Apr. 18, 2013
Investments-other						$ 75,000,000		$ 75,000,000					$ 0
Cash payment for purchase of royalty right																		$ 65,600,000
Revenue Recognition, Milestone Method, Revenue Recognized	$ 5,000,000		$ 6,000,000
Royalty rights						399,592,000	[1]	399,592,000	[1]				399,204,000	[2]
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%
Financing receivable, gross																					$ 20,000,000
Proceeds from Collection of Notes Receivable				$ 21,400,000				$ 54,653,000		$ 20,600,000
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						15.00%		15.00%
Fair Value Measurements, Sensitivity Analysis, Description								Should these discount rates increase or decrease by 2.5%, the fair value of the asset could decrease by $6.2 million or increase by $7.0 million, respectively. A third-party expert was engaged to help management develop its original estimate of the expected future cash flows. The estimated fair value of the asset is subject to variation should those cash flows vary significantly from those estimates. The Company periodically assesses the expected future cash flows and to the extent such payments are greater or less than its initial estimates, or the timing of such payments is materially different than the original estimates, the Company will adjust the estimated fair value of the asset. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase by $3.3 million or decrease by $3.3 million, respectively.
Royalty rights						$ 134,300,000		$ 134,300,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 134,300,000		$ 134,300,000
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						$ 14,800,000		$ 14,800,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 14,800,000		$ 14,800,000
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 $4.8 million or increase by $5.4 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase by $1.6 million or decrease by $1.6 million, respectively.
Royalty rights						$ 64,600,000		$ 64,600,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 64,600,000		$ 64,600,000
ARIAD [Member]
Annual royalty payment, maximum																	$ 20,000,000
Purchase of royalty rights																	100,000,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate						10.00%		10.00%
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 $7.6 million or increase by $8.6 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase by $2.5 million or decrease by $2.5 million, respectively.
Royalty rights						$ 100,100,000		$ 100,100,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 100,100,000		$ 100,100,000
Royalty Guarantees, Commitments, Amount																	200,000,000
ARIAD [Member] | Tranche 1 [Member]
Purchase of royalty rights																	50,000,000
ARIAD [Member] | Tranche two [Member]
Purchase of royalty rights																	50,000,000
ARIAD [Member] | Tranche 3 [Member]
Cash payment for purchase of royalty right												$ 40,000,000					$ 100,000,000
ARIAD [Member] | Low [Member]
Fixed royalty rate as a percentage of sales																	2.50%
ARIAD [Member] | High [Member]
Fixed royalty rate as a percentage of sales																	7.50%
AcelRx [Member]
Purchase of royalty rights																$ 65,000,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate						13.40%		13.40%
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 $10.2 million or increase by $12.6 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase by $1.9 million or decrease by $1.9 million, respectively
Royalty rights						$ 74,000,000		$ 74,000,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 74,000,000		$ 74,000,000
Percentage of royalty acquired																75.00%
Avinger Royalty Right [Member]
Fixed royalty rate as a percentage of sales															0.90%						1.80%
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate						15.00%		15.00%
Fair Value Measurements, Sensitivity Analysis, Description						Significant judgment is required in selecting the appropriate discount rate. Should this discount rate increase or decrease by 5%, the fair value of this asset could decrease by $73,000 or increase by $81,000, respectively. Should the expected royalties increase or decrease by 5%, the fair value of the asset could increase by $94,000 or decrease by $94,000, respectively.
Royalty rights						$ 1,900,000		$ 1,900,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 1,900,000		$ 1,900,000
Kybella [Member]
Purchase of royalty rights											$ 9,500,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate						14.40%		14.40%
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 $1.1 million or increase by $1.3 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase by $244,000 or decrease by $244,000, respectively
Royalty rights						$ 9,800,000		$ 9,800,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount						$ 9,800,000		$ 9,800,000
Maximum amount of additional funds, upon attainment of milestones		$ 1,000,000
Avinger [Member] | Notes Receivable [Member]
Amount company has agreed to advance under credit agreement					$ 40,000,000

[1] unaudited

[2] Note 1