Commitments and Contingencies - Additional Information (Details) - USD ($)				3 Months Ended			9 Months Ended
	Sep. 04, 2020	Jul. 14, 2020	Sep. 04, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Commitments And Contingencies [Line Items]
Operating leases, description							In January 2013, DermTech Operations entered into a non-cancelable lease agreement for its operating facilities. In January 2014, DermTech Operations signed an amendment to the lease to extend the term through January 2017. In November 2016, DermTech Operations signed a second amendment to the lease to extend the term through March 2022. In August 2019, DermTech Operations signed a third amendment to the lease to add additional space, and in September 2019, the Company signed a fourth amendment to the lease to add additional space. In February 2020, the Company signed a fifth amendment to the lease to add additional space. In connection with the Business Combination, the Company assumed all obligations under the lease, as amended, from DermTech Operations.
Tenant improvement allowance				$ 300,000			$ 300,000
Rent and common area maintenance expense				500,000		$ 200,000	1,300,000	$ 500,000
Payments for deferred underwriting fees							1,363,000
Underwriting fees									$ 1,363,000
Loss contingency, Aggregate value of common stock				2,000			2,000		$ 1,000
Issuance of preferred stock, total offering amount						718,000
Private placement
Commitments And Contingencies [Line Items]
Issuance of preferred stock, total offering amount					$ 23,891,000	$ 19,802,000
Private placement | LifeSci Capital LLC
Commitments And Contingencies [Line Items]
Issuance of preferred stock, total offering amount				1,011,000
Private placement | Settlement Agreement | LifeSci Capital LLC
Commitments And Contingencies [Line Items]
Loss contingency, Aggregate value of common stock		$ 1,000,000
Average closing market price, Common stock, Period	5 days	5 days
Loss contingency, Percentage of settlement amount in cash		50.00%
Loss contingency, Percentage of settlement amount in common shares		50.00%
Preferred stock, shares issued during period	87,790
Issuance of preferred stock, total offering amount	$ 1,000,000
Average closing price of common stock	$ 11.516
Cowen
Commitments And Contingencies [Line Items]
Payments for deferred underwriting fees			$ 800,000
Underwriting fees			$ 1,400,000	1,400,000			1,400,000
Proceeds from equity financing							15,000,000
Gross proceeds from PIPE financing							65,000,000
Deferred underwriting fee equity payable if equity financing limit not raised				$ 0			0
Maximum
Commitments And Contingencies [Line Items]
Increase in tenant improvement allowance							$ 100,000