Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2021	Jan. 31, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	001-38219
Entity Registrant Name	DECIPHERA PHARMACEUTICALS, INC.
Entity Address, State or Province	MA
City Area Code	781
Local Phone Number	209-6400
Title of 12(b) Security	Common Stock, $0.01 Par Value
Trading Symbol	DCPH
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Smaller Reporting Company	false
Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		58,552,372
Entity Public Float			$ 1,504,121,667
Documents Incorporated by Reference	Portions of the registrant's Proxy Statement for its 2022 Annual Meeting of Stockholders, which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the registrant's fiscal year ended December 31, 2021, are incorporated by reference into Part III of this Annual Report on Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001654151
Current Fiscal Year End Date	--12-31
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	30-1003521
Entity Address, City or Town	Waltham
Entity Address, Address Line One	200 Smith Street
Entity Address, Postal Zip Code	02451