Summary of Significant Accounting Policies - Narrative (Details) - USD ($)					1 Months Ended					3 Months Ended										12 Months Ended
	Oct. 01, 2019	Sep. 30, 2019	Aug. 08, 2017	Feb. 13, 2015	Mar. 31, 2017	Nov. 30, 2016	Jan. 31, 2016	Dec. 31, 2015	Feb. 28, 2015	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015	Jan. 01, 2019
Short-term Debt [Line Items]
Goodwill impairment																				$ 0	$ 0	$ 0
Advertising and marketing costs																				2,374,000	3,312,000	17,770,000
Proceeds from upfront license agreement payment																		$ 12,500,000				12,500,000
Total revenue										$ 48,258,000	$ 41,147,000	$ 56,702,000	$ 49,785,000	$ 56,053,000	$ 51,337,000	$ 59,296,000	$ 46,626,000			195,892,000	213,312,000	236,707,000
Cephalon, Inc.
Short-term Debt [Line Items]
Upfront cash proceeds for license agreement					$ 25,000,000		$ 30,000,000		$ 30,000,000										$ 30,000,000				$ 30,000,000
Licensing agreement, milestone proceeds							$ 15,000,000	$ 15,000,000
Licensing agreement, proceeds from unique billing code						$ 40,000,000
Royalty payments if product is approved, percentage of net sales (in percentage)	30.00%	25.00%		20.00%		25.00%
Teva Pharmaceuticals
Short-term Debt [Line Items]
Upfront cash proceeds for license agreement																				$ 9,000,000
Bendeka
Short-term Debt [Line Items]
Reporting term for partners' net product sales, royalty revenue																				25 days
Total revenue																				$ 31,182,000	24,568,000	16,225,000
License
Short-term Debt [Line Items]
Total revenue																				9,000,000	$ 0	$ 37,500,000
License | Teva Pharmaceuticals
Short-term Debt [Line Items]
Total revenue																				$ 9,000,000
Teva Pharmaceuticals | Cephalon, Inc.
Short-term Debt [Line Items]
Milestone payment benchmark, net sales					$ 500,000,000
Minimum | Accounting Standards Update 2016-02
Short-term Debt [Line Items]
Operating lease obligation																								$ 3,000,000
Maximum | Accounting Standards Update 2016-02
Short-term Debt [Line Items]
Operating lease obligation																								$ 4,000,000
Line of Credit | Amendment Credit Agreement
Short-term Debt [Line Items]
Credit agreement, term			3 years