Convertible Preferred Stock - Narrative (Details)			12 Months Ended
	Apr. 04, 2018 USD ($)	Mar. 26, 2018 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) segment $ / shares Rate shares	Dec. 31, 2020 $ / shares shares	Feb. 11, 2020 shares
Class of Stock [Line Items]
Preferred stock automatically converts into aggregate net proceeds (at least) | $			$ 40,000,000
Underwritten public offering of common stock, minimum aggregate net proceeds | $			$ 40,000,000
Minimum ratio offering price per share of OIP | Rate			150.00%
Series 1 Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued (in shares) | shares			12,433,953	0	51,680,254
Convertible preferred stock, par value (in usd per share)			$ 0.0001	$ 0.0001
Convertible preferred stock, liquidation rights per share (in usd per share)			3.217
Convertible preferred stock, dividend rate (in usd per share)			$ 0.25736
Number of common stock shares converted per preferred share (in shares) | shares			10
Series 1 Preferred Stock | KKR Phorm Investors L.P. (KKR)
Class of Stock [Line Items]
Convertible preferred stock, shares issued (in shares) | shares			12,433,953
Convertible preferred stock, par value (in usd per share)			$ 0.001
Convertible preferred stock, price per share (in usd per share)			$ 3.217
Issuance of preferred stock | $			$ 40,000,000
Series 2 Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued (in shares) | shares			7,499,996	0	38,760,190
Convertible preferred stock, par value (in usd per share)			$ 0.0001	$ 0.0001
Convertible preferred stock, liquidation rights per share (in usd per share)			4.00
Convertible preferred stock, dividend rate (in usd per share)			0.32
Series 2 Preferred Stock | KKR Phorm Investors L.P. (KKR)
Class of Stock [Line Items]
Convertible preferred stock, par value (in usd per share)			0.001
Convertible preferred stock, price per share (in usd per share)			$ 4.00
Issuance of preferred stock | $			$ 30,000,000
Series 2 Preferred Stock | Other Investors | KKR Phorm Investors L.P. (KKR)
Class of Stock [Line Items]
Convertible preferred stock, shares issued (in shares) | shares			7,499,996
Other investors with a small percentage			0.02%
Series 3 Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued (in shares) | shares		4,000,000	4,000,000	0	31,850,304
Convertible preferred stock, par value (in usd per share)		$ 0.001	$ 0.0001	$ 0.0001
Convertible preferred stock, price per share (in usd per share)		$ 4.00
Issuance of preferred stock | $	$ 16,000,000	$ 16,000,000
Convertible preferred stock, liquidation rights per share (in usd per share)			4.00
Convertible preferred stock, dividend rate (in usd per share)			$ 0.32
Number of votes per share of common stock | segment			10
Series 3 Preferred Stock | Other Investors
Class of Stock [Line Items]
Other investors with a small percentage		0.02%
Series 3 Preferred Stock | Nexperia
Class of Stock [Line Items]
Other investors with a small percentage		9.90%