Debt (Schedule Of General Information Of Financing Transaction) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2022		Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Secured financing		$ 3,756,400,000		$ 3,811,500,000
Restricted cash and cash equivalents		$ 410,000,000.0		410,900,000	$ 380,200,000
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		n/a
Debt maturity date		Jun. 22, 2025
Financing Amount	[1]	$ 410,000,000
Revolving Secured Line Of Credit [Member] | BSBY [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		187.50%
Revolving Secured Line Of Credit [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		87.50%
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	CAC Warehouse Funding LLC II
Debt maturity date	[2],[3]	Apr. 30, 2024
Debt financing amount		$ 400,000,000.0	[2],[4]	400,000,000.0
Secured financing		0		0
Loans pledged as collateral		0		0
Restricted cash and cash equivalents		$ 1,000,000.0		$ 1,000,000.0
Interest rate		0.00%		0.00%
Warehouse Facility II [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[4]	175.00%
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	CAC Warehouse Funding LLC IV
Debt maturity date	[2],[3]	May 20, 2025
Debt financing amount		$ 300,000,000.0	[2],[4]	$ 300,000,000.0
Secured financing				0
Loans pledged as collateral		0		0
Restricted cash and cash equivalents		$ 1,000,000.0		$ 1,000,000.0
Interest rate		0.00%		0.00%
Warehouse Facility IV [Member] | SOFR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[4]	221.40%
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	CAC Warehouse Funding LLC V
Debt maturity date	[2],[5]	Dec. 29, 2025
Debt financing amount		$ 200,000,000.0	[2],[4]	$ 125,000,000.0
Secured financing		0
Loans pledged as collateral		0		0
Restricted cash and cash equivalents		$ 1,000,000.0		$ 1,000,000.0
Interest rate		0.00%		0.00%
Warehouse Facility V [Member] | SOFR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[4]	245.00%
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	CAC Warehouse Funding LLC VI
Debt maturity date	[2],[3]	Sep. 30, 2024
Debt financing amount	[2]	$ 75,000,000.0
Secured financing		0		$ 0
Loans pledged as collateral		0		0
Restricted cash and cash equivalents		$ 0		$ 0
Interest rate		0.00%		0.00%
Warehouse Facility VI [Member] | BSBY [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[4]	200.00%
Warehouse Facility VIII [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	CAC Warehouse Funding LLC VIII
Debt maturity date	[2],[3]	Sep. 01, 2024
Debt financing amount		$ 200,000,000.0	[2],[4]	$ 200,000,000.0
Secured financing		0		0
Loans pledged as collateral		0		0
Restricted cash and cash equivalents		$ 0		$ 0
Interest rate		0.00%		0.00%
Warehouse Facility VIII [Member] | SOFR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[4]	201.40%
Term ABS 2019-1 [Member]
Debt Instrument [Line Items]
Secured financing		$ 0		$ 124,600,000
Loans pledged as collateral		0		292,400,000
Restricted cash and cash equivalents		$ 0		$ 31,800,000
Interest rate		0.00%		3.86%
Term ABS 2019-2 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2019-2
Debt maturity date	[2],[6]	Aug. 15, 2025
Debt financing amount	[2]	$ 500,000,000.0
Secured financing		500,000,000.0		$ 500,000,000.0
Loans pledged as collateral		627,500,000		582,100,000
Restricted cash and cash equivalents		$ 51,000,000.0		$ 50,700,000
Interest rate		5.15%		3.13%
Term ABS 2019-3 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2019-3
Debt maturity date	[2],[3]	Nov. 15, 2021
Debt financing amount	[2]	$ 351,700,000
Secured financing		64,400,000		$ 323,900,000
Loans pledged as collateral		200,900,000		382,900,000
Restricted cash and cash equivalents		$ 24,500,000		$ 36,500,000
Interest rate		3.00%		2.58%
Term ABS 2020-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2020-1
Debt maturity date	[2],[3]	Feb. 15, 2022
Debt financing amount	[2]	$ 500,000,000.0
Secured financing		144,600,000		$ 500,000,000.0
Loans pledged as collateral		362,500,000		591,600,000
Restricted cash and cash equivalents		$ 38,800,000		$ 51,900,000
Interest rate		2.51%		2.18%
Term ABS 2020-2 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2020-2
Debt maturity date	[2],[3]	Jul. 15, 2022
Debt financing amount	[2]	$ 481,800,000
Secured financing		307,000,000.0		$ 481,800,000
Loans pledged as collateral		452,000,000.0		579,500,000
Restricted cash and cash equivalents		$ 43,900,000		$ 50,100,000
Interest rate		1.81%		1.65%
Term ABS 2020-3 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2020-3
Debt maturity date	[2],[3]	Oct. 17, 2022
Debt financing amount	[2]	$ 600,000,000.0
Secured financing		520,700,000		$ 600,000,000.0
Loans pledged as collateral		655,100,000		688,100,000
Restricted cash and cash equivalents		$ 53,900,000		$ 58,400,000
Interest rate		1.47%		1.44%
Term ABS 2021-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2021-1
Debt maturity date	[2],[3]	Dec. 16, 2024
Debt financing amount		$ 100,000,000.0	[2],[4]	$ 100,000,000.0
Secured financing		100,000,000.0		100,000,000.0
Loans pledged as collateral		115,000,000.0		143,700,000
Restricted cash and cash equivalents		$ 8,500,000		$ 10,200,000
Interest rate		6.52%		2.10%
Term ABS 2021-1 [Member] | SOFR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	[4]	220.00%
Term ABS 2021-2 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2021-2
Debt maturity date	[2],[3]	Feb. 15, 2023
Debt financing amount	[2]	$ 500,000,000.0
Secured financing		500,000,000.0		$ 500,000,000.0
Loans pledged as collateral		572,900,000		618,700,000
Restricted cash and cash equivalents		$ 44,500,000		$ 49,200,000
Interest rate		1.12%		1.12%
Term ABS 2021-3 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2021-3
Debt maturity date	[2],[3]	May 15, 2023
Debt financing amount	[2]	$ 450,000,000.0
Secured financing		450,000,000.0		$ 450,000,000.0
Loans pledged as collateral		519,900,000		619,800,000
Restricted cash and cash equivalents		$ 38,800,000		$ 46,500,000
Interest rate		1.14%		1.14%
Term ABS 2021-4 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Credit Acceptance Funding LLC 2021-4
Debt maturity date	[2],[3]	Oct. 16, 2023
Debt financing amount	[2]	$ 250,100,000
Secured financing		250,100,000		$ 250,100,000
Loans pledged as collateral		278,500,000		281,200,000
Restricted cash and cash equivalents		$ 21,800,000		$ 22,100,000
Interest rate		1.44%		1.44%
Term ABS 2022-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		Credit Acceptance Funding LLC 2022-1
Debt maturity date		Jun. 17, 2024
Debt financing amount		$ 350,000,000.0
Secured financing		350,000,000.0
Loans pledged as collateral		434,700,000		$ 0
Restricted cash and cash equivalents		$ 27,700,000
Interest rate		5.03%
Term ABS 2022-2 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		Credit Acceptance Funding LLC 2022-2
Debt maturity date		Dec. 15, 2025
Debt financing amount		$ 200,000,000.0
Secured financing		200,000,000.0
Loans pledged as collateral		229,300,000		0
Restricted cash and cash equivalents		$ 25,600,000
Interest rate		6.65%
Term ABS 2022-2 [Member] | SOFR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		235.00%
Term ABS 2022-3 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		Credit Acceptance Funding LLC 2022-3
Debt maturity date		Oct. 15, 2024
Debt financing amount		$ 389,900,000
Secured financing		389,900,000
Loans pledged as collateral		429,200,000		$ 0
Restricted cash and cash equivalents		$ 27,600,000
Interest rate		7.68%
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		n/a
Debt maturity date		Dec. 31, 2024
Debt financing amount		$ 400,000,000.0
Interest rate		5.125%		5.125%
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		n/a
Debt maturity date		Mar. 15, 2026
Debt financing amount		$ 400,000,000.0
Interest rate		6.625%		6.625%
Mortgage [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	[2]	Chapter 4 Properties, LLC
Debt maturity date	[2]	Aug. 06, 2028
Debt financing amount	[2]	$ 9,000,000.0
Interest rate		5.46%		1.60%
Mortgage [Member] | BSBY [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		150.00%

[1] The amount of the facility will decrease by $25.0 million on June 22, 2023.

[2] Financing made available only to a specified subsidiary of the Company.

[3] Represents the revolving maturity date. The outstanding balance will amortize after the revolving maturity date based on the cash flows of the pledged assets.

[4] Interest rate cap agreements are in place to limit the exposure to increasing interest rates.

[5] Represents the revolving maturity date. The outstanding balance will amortize after the revolving maturity date and any amounts remaining on December 27, 2027 will be due on that date.

[6] Represents the revolving maturity date. The Company has the option to redeem and retire the indebtedness after the revolving maturity date. If we do not elect this option, the outstanding balance will amortize based on the cash flows of the pledged assets.