Fair Value Measurements (Narrative) (Detail) $ / shares in Units, shares in Millions				3 Months Ended		12 Months Ended
		Aug. 02, 2018 USD ($)	Jul. 08, 2016 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Aug. 03, 2018 USD ($)	Jul. 09, 2016 USD ($)	Dec. 31, 2015 $ / shares	Dec. 15, 2015 shares	Sep. 18, 2015 USD ($)	Nov. 06, 2014 USD ($)	Jun. 26, 2014 USD ($)	Oct. 18, 2013 USD ($)
Intangible Assets, Net (Excluding Goodwill)	[1]			$ 12,884,000			$ 13,186,000
Investment Owned, at Cost				6,600,000			6,600,000
Financing Receivable, before Allowance for Credit Loss, Noncurrent				$ 52,081,000
Cash payment for purchase of royalty right													$ 65,600,000
Purchase of royalty rights		$ 20,000,000
Reversionary interest period								$ 481,000,000
Sensitivity range for royalty disclosures				2.50%
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%
Revenues				5,995,000	$ 6,696,000
Finite-Lived Intangible Assets, Gross				16,115,000			16,115,000
Asset Impairment Charges				0		$ 8,200,000
Convertible Notes Payable, Carrying Value				13,302,000			27,250,000
Notes Payable, Fair Value Disclosure				$ 15,900,000			33,900,000
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
Cash flow model expected royalty sales term				9 years
Sensitivity - decrease in fair value from increase in discount rate				$ (17,100,000)
Sensitivity - increase in fair value from decrease in discount rate				20,000,000
Sensitivity to increase or decrease in expected royalty				5,400,000
Royalty rights				210,800,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				$ 210,800,000
Contractual cap on potential royalty asset multiple				2
VB [Member]
Purchase of royalty rights														$ 15,500,000
Cash flow model expected royalty sales term				10 years
Sensitivity - decrease in fair value from increase in discount rate				$ (1,300,000)
Sensitivity - increase in fair value from decrease in discount rate				1,500,000
Sensitivity to increase or decrease in expected royalty				$ 300,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				15.00%
Royalty rights				$ 13,500,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				$ 13,500,000
Contractual cap on potential royalty asset multiple				2.3
University of Michigan [Member]
Cash flow model expected royalty sales term				2 years
Sensitivity - decrease in fair value from increase in discount rate				$ (500,000)
Sensitivity - increase in fair value from decrease in discount rate				500,000
Sensitivity to increase or decrease in expected royalty				$ 500,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				12.80%
Royalty rights				$ 18,600,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				$ 18,600,000
AcelRx [Member]
Purchase of royalty rights												$ 65,000,000
Cash flow model expected royalty sales term				13 years
Sensitivity - decrease in fair value from increase in discount rate				$ (1,200,000)
Sensitivity - increase in fair value from decrease in discount rate				1,400,000
Sensitivity to increase or decrease in expected royalty				$ 300,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				13.40%
Royalty rights				$ 12,900,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				$ 12,900,000
Percentage of royalty acquired												75.00%
Percentage of first four milestone payments acquired												80.00%
Number of potential milestone royalties												4
Contractual cap on potential royalty asset multiple				3
Kybella [Member]
Purchase of royalty rights									$ 9,500,000
Cash flow model expected royalty sales term				6 years
Sensitivity - increase in fair value from decrease in discount rate				$ 100,000
Sensitivity to increase or decrease in expected royalty				$ 100,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				14.40%
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				$ 500,000
Maximum amount of additional funds, upon attainment of milestones			$ 1,000,000
Alphaeon [Member]
Investment Owned, Balance, Shares | shares											1.7
Investment estimated fair value, per share | $ / shares										$ 3.84
Minimum [Member] | Depomed [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				10.00%
Maximum [Member] | Depomed [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				24.00%
Income generating assets [Member]
Revenues				$ 10,000	(30,000)
Pharmaceutical [Member]
Revenues				0	0
Discontinued Operations, Held-for-sale [Member]
Increase (Decrease) in Assets Held-for-sale				(12,761,000)	0
Intangible Assets, Net (Excluding Goodwill)				9,723,000			10,112,000
Loss on classification as held for sale				(12,483,000)			0
Royalty rights				262,021,000			266,196,000
Revenues				24,425,000	$ 32,218,000
Discontinued Operations, Held-for-sale [Member] | Depomed [Member]
Increase (Decrease) in Assets Held-for-sale				4,700,000
Discontinued Operations, Held-for-sale [Member] | VB [Member]
Increase (Decrease) in Assets Held-for-sale				300,000
Discontinued Operations, Held-for-sale [Member] | University of Michigan [Member]
Increase (Decrease) in Assets Held-for-sale				400,000
Discontinued Operations, Held-for-sale [Member] | AcelRx [Member]
Increase (Decrease) in Assets Held-for-sale				300,000
Discontinued Operations, Held-for-sale [Member] | Kybella [Member]
Increase (Decrease) in Assets Held-for-sale				100,000
Discontinued Operations, Held-for-sale [Member] | Income generating assets [Member]
Increase (Decrease) in Assets Held-for-sale				5,800,000
Discontinued Operations, Held-for-sale [Member] | Pharmaceutical [Member]
Estimated cost to sell				1,800,000
Loss on classification as held for sale, fair value adjustment				4,900,000
Loss on classification as held for sale				$ 6,700,000
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate				19.00%
Fair Value Level 3 [Member]
Royalty rights				$ 262,021,000			$ 266,196,000
Notes Receivable, Fair Value Disclosure				$ 57,279,000

[1] unaudited