Debt (Schedule Of General Information Of Financing Transaction) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Jan. 22, 2014
Debt Instrument [Line Items]
Maturity date	Sep. 10, 2017
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	n/a
Maturity date	Jun. 23, 2016
Financing Amount	$ 235,000,000
Revolving Secured Line Of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.875%
Revolving Secured Line Of Credit [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	0.875%
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	CAC Warehouse Funding Corp. II	[1]
Debt maturity date	Dec. 27, 2015	[1],[2]
Debt financing amount	325,000,000	[1]
Warehouse Facility II [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%	[1],[3]
Warehouse Facility III [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	CAC Warehouse Funding III, LLC	[1]
Debt maturity date	Sep. 10, 2015	[1],[4]
Debt financing amount	75,000,000	[1]
Warehouse Facility III [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.60%	[1],[3]
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	CAC Warehouse Funding LLC IV	[1]
Debt maturity date	Apr. 05, 2016	[1],[2]
Debt financing amount	75,000,000	[1]
Warehouse Facility IV [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%	[1],[3]
Term ABS 2011-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	Credit Acceptance Funding LLC 2011-1	[1]
Debt maturity date	Sep. 16, 2013	[1],[2]
Debt financing amount	200,500,000	[1]
Term ABS 2012-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	Credit Acceptance Funding LLC 2012-1	[1]
Debt maturity date	Mar. 17, 2014	[1],[2]
Debt financing amount	201,300,000	[1]
Term ABS 2012-2 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	Credit Acceptance Funding LLC 2012-2	[1]
Debt maturity date	Sep. 15, 2014	[1],[2]
Debt financing amount	252,000,000	[1]
Term ABS 2013-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	Credit Acceptance Funding LLC 2013-1	[1]
Debt maturity date	Apr. 15, 2015	[1],[2]
Debt financing amount	140,300,000	[1]
Term ABS 2013-2 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	Credit Acceptance Funding LLC 2013-2	[1]
Debt maturity date	Oct. 15, 2015	[1],[2]
Debt financing amount	197,800,000	[1]
2021 Senior Notes [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary	n/a
Debt maturity date	Feb. 15, 2021
Debt financing amount	$ 300,000,000		$ 300,000,000

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

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

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

[4] Represents the revolving maturity date.  The outstanding balance will amortize after the revolving maturity date and any amounts remaining on September 10, 2017 will be due.