Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 04, 2021	Jun. 30, 2020
Document And Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	000-20202
Entity Registrant Name	CREDIT ACCEPTANCE CORP
Entity Central Index Key	0000885550
Entity Incorporation, State or Country Code	MI
Entity Tax Identification Number	38-1999511
Entity Address, Address Line One	25505 W. Twelve Mile Road
Entity Address, City or Town	Southfield,
Entity Address, State or Province	MI
Entity Address, Postal Zip Code	48034-8339
City Area Code	248
Local Phone Number	353-2700
Title of 12(b) Security	Common Stock, $.01 par value
Trading Symbol	CACC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 4,142.7
Entity Common Stock, Shares Outstanding		16,818,933
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false