Stock-Based Compensation Plans - Summary of Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Employee Stock Options, Vital Therapies Inc.
Options
Outstanding, Beginning balance (in shares) | shares	14,403
Granted (in shares) | shares	0
Exercised (in shares) | shares	0
Forfeited or expired (in shares) | shares	(14,403)
Outstanding, Ending balance (in shares) | shares	0
Options vested and expected to vest, Ending balance (in shares) | shares	0
Options exercisable, Ending balance (in shares) | shares	0
Weighted- Average Exercise Price
Outstanding, Beginning balance (usd per share) | $ / shares	$ 306.01
Granted (usd per share) | $ / shares	0
Exercised (usd per share) | $ / shares	0
Forfeited or expired (usd per share) | $ / shares	306.01
Outstanding, Ending balance (usd per share) | $ / shares	0
Options vested and expected to vest, Weighted-Average Exercise Price, Ending balance (usd per share) | $ / shares	0
Options exercisable, Weighted-Average Exercise Price, Ending balance (usd per share) | $ / shares	$ 0
Other Disclosures
Outstanding, Weighted-Average Remaining Contractual Term, Ending balance	0 years
Options vested and expected to vest , Weighted-Average Remaining Contractual Term, Ending balance	0 years
Options exercisable, Weighted-Average Remaining Contractual Term, Ending balance	0 years
Outstanding, Aggregate Intrinsic Value, Ending balance | $	$ 0
Options vested and expected to vest , Aggregate Intrinsic Value, Ending balance | $	0
Options exercisable, Aggregate Intrinsic Value, Ending balance | $	$ 0
2019 Omnibus Equity Incentive Plan | Outstanding stock options
Options
Outstanding, Beginning balance (in shares) | shares	456,645
Granted (in shares) | shares	597,068
Exercised (in shares) | shares	0
Forfeited or expired (in shares) | shares	(83,891)
Outstanding, Ending balance (in shares) | shares	969,822
Options vested and expected to vest, Ending balance (in shares) | shares	969,822
Options exercisable, Ending balance (in shares) | shares	167,515
Weighted- Average Exercise Price
Outstanding, Beginning balance (usd per share) | $ / shares	$ 12.57
Granted (usd per share) | $ / shares	12.24
Exercised (usd per share) | $ / shares	0
Forfeited or expired (usd per share) | $ / shares	13.32
Outstanding, Ending balance (usd per share) | $ / shares	12.31
Options vested and expected to vest, Weighted-Average Exercise Price, Ending balance (usd per share) | $ / shares	12.31
Options exercisable, Weighted-Average Exercise Price, Ending balance (usd per share) | $ / shares	$ 12.51
Other Disclosures
Outstanding, Weighted-Average Remaining Contractual Term, Ending balance	9 years 4 months 28 days
Options vested and expected to vest , Weighted-Average Remaining Contractual Term, Ending balance	9 years 4 months 28 days
Options exercisable, Weighted-Average Remaining Contractual Term, Ending balance	8 years 10 months 24 days
Outstanding, Aggregate Intrinsic Value, Ending balance | $	$ 6,075,771
Options vested and expected to vest , Aggregate Intrinsic Value, Ending balance | $	6,075,771
Options exercisable, Aggregate Intrinsic Value, Ending balance | $	$ 1,015,048