Fair Value Measurements (Narrative) (Detail) - USD ($)						1 Months Ended	3 Months Ended
	Dec. 13, 2016	Sep. 21, 2016	Jul. 08, 2016	Jun. 02, 2016	Sep. 22, 2015	Apr. 30, 2013	Mar. 31, 2017		Mar. 31, 2016	Mar. 30, 2017	Dec. 31, 2016		Jul. 09, 2016	Sep. 23, 2015	Sep. 18, 2015	Jul. 28, 2015	Nov. 06, 2014	Jun. 26, 2014	Oct. 18, 2013	Apr. 18, 2013
Accounts and Notes Receivable, Net							$ 95,300,000				$ 105,300,000
Investments-other							75,000,000				75,000,000
Cash payment for purchase of royalty right																	$ 65,600,000
Change of ownership repayment										$ 108,200,000
Revenue Recognition, Milestone Method, Revenue Recognized	$ 6,000,000	$ 5,000,000		$ 6,000,000
Royalty rights							293,801,000	[1]			402,318,000	[2]
Transfers from level 1 to level 2, amount							0				0
Transfers from level 2 to level 1, amount							0				0
Percentage of royalty acquired																	75.00%
Financing receivable, gross																				$ 20,000,000
Proceeds from Collection of Notes Receivable					$ 21,400,000		7,890,000		$ 0
Notes Receivable, Fair Value Disclosure							$ 96,500,000				$ 107,400,000
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%
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 $12.2 million or increase by $13.9 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 or decrease by $4.0 million, respectively.
Royalty rights							$ 161,600,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount							$ 161,600,000
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 $1.2 million or increase by $1.4 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase or decrease by $0.4 million, respectively.
Royalty rights							$ 15,200,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount							$ 15,200,000
University of Michigan [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate							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 $2.3 million or increase by $2.5 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase or decrease by $0.9 million, respectively.
Royalty rights							$ 35,700,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount							$ 35,700,000
ARIAD [Member]
Purchase of royalty rights																$ 100,000,000
Royalty Guarantees, Commitments, Amount																200,000,000
ARIAD [Member] | Tranche 1 [Member]
Purchase of royalty rights																50,000,000
ARIAD [Member] | Tranche 3 [Member]
Cash payment for purchase of royalty right																$ 100,000,000
AcelRx [Member]
Purchase of royalty rights															$ 65,000,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate							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 $12.8 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase or decrease by $1.7 million, respectively
Royalty rights							$ 69,600,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount							$ 69,600,000
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%
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 $41,000 or increase by $44,000, respectively. Should the expected royalties increase or decrease by 5%, the fair value of the asset could increase or decrease by $35,000, respectively.
Royalty rights							$ 1,400,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount							$ 1,400,000
Kybella [Member]
Purchase of royalty rights													$ 9,500,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate							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 $1.0 million or increase by $1.2 million, respectively. Should the expected royalties increase or decrease by 2.5%, the fair value of the asset could increase or decrease by $258,000, respectively
Royalty rights							$ 10,300,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount							$ 10,300,000
Maximum amount of additional funds, upon attainment of milestones			$ 1,000,000
Avinger [Member]
Proceeds from Collection of Notes Receivable					$ 21,400,000
Avinger [Member] | Notes Receivable [Member]
Amount company has agreed to advance under credit agreement						$ 40,000,000

[1] unaudited

[2] Note 1