Commitments and Contingencies - Additional Information (Details) - USD ($)			3 Months Ended	9 Months Ended
	Oct. 11, 2019	May 07, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Commitments And Contingencies [Line Items]
Common stock fair value				$ 3,000		$ 2,000
Common stock, shares issued				28,964,506		28,964,506
Common stock, shares authorized	50,000,000			400,000,000		400,000,000
Fair value adjustment of warrants			$ 57,776,000	$ (95,000)	$ 59,060,000
Takeda License | Takeda
Commitments And Contingencies [Line Items]
License agreement description				The agreement will remain in effect, on a country-by-country and product-by-product basis, until the later of (i) the expiration of the last to expire valid patent claim covering vonoprazan fumarate alone or in combination with at least one other therapeutically active ingredient, (ii) the expiration of the applicable regulatory exclusivity and (iii) 15 years from the date of first commercial sale, unless earlier terminated. The Company may terminate the Takeda License upon six months’ written notice. The Company and Takeda may terminate the Takeda License in the case of the other party’s insolvency or material uncured breach. Takeda may terminate the Takeda License if the Company challenges, or assists in challenging, licensed patents.
Agreement expiration term from date of first commercial sale		15 years
Cash consideration paid for license		$ 25,000,000
Common stock fair value		$ 5,900,000
Common stock, shares issued		1,084,000
Warrants exercise price		$ 0.00004613
Initial fair value of warrants		$ 47,900,000
Additional warrant issued		0
Maximum amount payable in sales milestones upon achievement of specified levels of product sales		$ 250,000,000
Transaction costs		$ 100,000
Warrants expiration date		May 07, 2029
Fair value adjustment of warrants	$ 144,200,000
Takeda License | Takeda | Common Stock
Commitments And Contingencies [Line Items]
Warrants issued to purchase shares		7,588,000