Debt (Schedule of General Information of Financing Transaction) (Details) (USD $)	0 Months Ended	6 Months Ended
	Jan. 22, 2014	Jun. 30, 2014		Jan. 22, 2014
Debt Instrument [Line Items]
Line of credit maturity date		Sep. 10, 2017
Revolving Secured Line of Credit [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		n/a
Line of credit maturity date		Jun. 23, 2017
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 facility 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 facility 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 facility 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 facility financing amount		200,500,000.0	[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 facility financing amount		201,300,000.0	[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 facility 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 facility financing amount		140,300,000.0	[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 facility financing amount		197,800,000.0	[1]
Term ABS 2014-1 [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		Credit Acceptance Funding LLC 2014-1	[1]
Debt maturity date		Apr. 15, 2016	[1],[2]
Debt facility financing amount		299,000,000	[1]
2021 Senior Notes [Member]
Debt Instrument [Line Items]
Wholly-owned Subsidiary		n/a
Debt maturity date	Feb. 15, 2021	Feb. 15, 2021
Debt facility 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.