Fair Value Measurements (Narrative) (Detail) $ / shares in Units, shares in Millions				2 Months Ended	3 Months Ended						8 Months Ended	12 Months Ended
	May 15, 2020	Jan. 07, 2018 USD ($)	Jul. 08, 2016 USD ($)	Aug. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) numberOfNotesRecivables $ / shares shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Aug. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) numberOfNotesRecivables $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 30, 2019 USD ($)	Aug. 01, 2018 USD ($)	Jun. 27, 2018 USD ($)	Jul. 09, 2016 USD ($)	Sep. 18, 2015 USD ($)	Nov. 06, 2014 USD ($)	Jun. 26, 2014 USD ($)	Oct. 18, 2013 USD ($)
Asset Impairment Charges											$ 0		$ 10,768,000	$ 8,200,000
Intangible assets, net							$ 13,186,000						13,186,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				$ 217,913,000			266,196,000				217,913,000		266,196,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											(4,350,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(43,933,000)
Cash payment for purchase of royalty right																				$ 65,600,000
Proceeds from Legal Settlements												$ 7,500,000
Royalty rights - at fair value							266,196,000						266,196,000
Percentage of royalty acquired																				75.00%
Revenues				4,115,000	$ 5,211,000	$ 5,995,000	8,521,000	$ 8,031,000	$ 7,458,000	$ 6,696,000	15,321,000		30,706,000	32,028,000
Maximum amount of additional funds, upon attainment of milestones		$ 2,000,000.0
Change in fair value of acquired royalty rights, Level 3 Rollforward											(8,804,000)		(31,042,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements											0		0	(858,000)
Notes Receivable, Fair Value Disclosure							57,300,000					$ 700,000	57,300,000
Gain (Loss) on Disposition of Assets											0		3,476,000	0
Notes Payable, Carrying Value							27,250,000						27,250,000
Assets, Fair Value							$ 493,879,000						$ 493,879,000
Number Of Notes Receivable Assets | numberOfNotesRecivables							2						2
Transfers from level 1 to level 2, amount				0			$ 0				0		$ 0
Transfers from level 2 to level 1, amount				0			0				0		0
Fair Value Level 2 [Member]
Royalty rights - at fair value							0						0
Notes payable, Fair Value							33,931,000						33,931,000
Assets, Fair Value							14,152,000						14,152,000
Fair Value Level 3 [Member]
Royalty rights - at fair value							266,196,000						266,196,000
Notes Receivable, Fair Value Disclosure							57,279,000						57,279,000
Notes payable, Fair Value							0						0
Assets, Fair Value							266,196,000						266,196,000
Royalty right [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				217,913,000			266,196,000				217,913,000		266,196,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											(4,350,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(43,933,000)
Estimated cost to sell				4,600,000							4,600,000
Assets [Member]
Assets, Fair Value							52,081,000						52,081,000
Assets [Member] | Fair Value Level 2 [Member]
Notes Receivable, Fair Value Disclosure							0						0
Noden [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate					17.00%	19.00%
Loss on classification as held for sale						$ 6,700,000
Estimated cost to sell						1,800,000
Increase (Decrease) in Assets Held-for-sale					$ 16,800,000	$ 4,900,000
VB [Member]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount																					$ 15,500,000
Royalty asset multiple												2.3
Payments for (Proceeds from) Productive Assets											(4,200,000)
Gain (Loss) on Disposition of Assets											0
VB [Member] | Royalty right [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				0			$ 13,590,000				0		$ 13,590,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											(4,182,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(9,408,000)
U-M
Cash flow model expected royalty sales term							3 years
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate							12.80%						12.80%
U-M | Royalty right [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				17,450,000			$ 20,398,000				17,450,000		$ 20,398,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(2,948,000)
Depomed [Member]
Cash payment for purchase of royalty right																$ 20,000,000.0						$ 240,500,000
Maximum royalty prior to amendment																						481,000,000.0
Cash flow model expected royalty sales term							9 years
Purchase of royalty right																						241,300,000
Royalty right purchase transaction costs																						$ 800,000
Depomed [Member] | Royalty right [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				200,463,000			$ 218,672,000				200,463,000		218,672,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(18,209,000)
AcelRx [Member]
Purchase of royalty right																			$ 65,000,000.0
Percentage of royalty acquired																			75.00%
Payments for (Proceeds from) Productive Assets											0
Gain (Loss) on Disposition of Assets											0
Royalty Rights, Period To Give Notice To Terminate License Agreement	180 days
AcelRx [Member] | Royalty right [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				0			12,952,000				0		12,952,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(12,952,000)
Kybella [Member]
Purchase of royalty right																		$ 9,500,000
Maximum amount of additional funds, upon attainment of milestones			$ 1,000,000.0
Payments for (Proceeds from) Productive Assets											(200,000)
Gain (Loss) on Disposition of Assets											0
Kybella [Member] | Royalty right [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				0			$ 584,000				0		$ 584,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales											(168,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings											(416,000)
Assertio | Royalty right [Member]
Liquidation Basis of Accounting, Expected Cash Realizable Value, Royalty Asset												$ 204,500,000
Cerdelga | Royalty right [Member]
Liquidation Basis of Accounting, Expected Cash Realizable Value, Royalty Asset												15,500,000
Alphaeon [Member]
Investment Owned, Balance, Shares | shares							1.7						1.7
Investment estimated fair value, per share | $ / shares							$ 3.84						$ 3.84
Investment Owned, at Fair Value				$ 1,000,000.0			$ 6,600,000				1,000,000.0		$ 6,600,000
Liquidating Basis of Accounting, Expected Cash Realizable Value, Assets												1,000,000.0
Noden [Member]
Impairment of Intangible Assets, Finite-lived													152,300,000
Intangible Assets, Gross (Excluding Goodwill)							$ 10,100,000					10,100,000	10,100,000		$ 32,600,000		$ 192,500,000
Intangible assets, net									$ 40,100,000
CareView [Member]
Asset Impairment Charges											0		$ 10,800,000	8,200,000
Minimum [Member] | Depomed [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate							10.00%						10.00%
Maximum [Member] | Depomed [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate							24.00%						24.00%
Discontinued Operations, Held-for-sale [Member]
Impairment of Intangible Assets, Finite-lived											0	$ 22,500,000	$ 22,490,000	152,330,000
Intangible assets, net							$ 10,112,000						10,112,000
Royalty rights - at fair value							$ 266,196,000						266,196,000
Revenues											20,675,000		24,051,000	166,083,000
Payments for (Proceeds from) Productive Assets											(35,129,000)
Increase (Decrease) in Assets Held-for-sale											$ (28,904,000)		$ 0	$ 0