Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($)			1 Months Ended		5 Months Ended		12 Months Ended
	Aug. 10, 2017	Dec. 13, 2016	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Revenue Recognition, Milestone Method [Line Items]
Proceeds from license fees received				$ 500,000
License fees received, period of monthly fees				1 year
Required contributions of development regulatory and commercialization costs					$ 2,500,000
Recognition of licensing fees								$ 180,000
Royalty and licensing revenue					$ 11,696,676	$ 14,831,000	$ 18,406,142	5,097,595
Milestone revenue recognized								4,500,000
Royalty revenue, excluding milestone revenue recognized								$ 418,000
SWK Purchase Agreement
Revenue Recognition, Milestone Method [Line Items]
Legal fees		$ 40,000					40,000
Milestone payment receivable under purchase agreement		3,750,000					3,750,000
Proceeds from royalties received	$ 3,750,000		$ 13,710,000				17,460,000
Upfront purchase price received under purchase agreement		$ 13,750,000					$ 13,750,000