Automobile Loan Receivables - Credit Quality Indicators (Details)	Jun. 30, 2011	Dec. 31, 2010
Consumer Credit Score [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	100.00%	100.00%
Fico Score Lower than 580 [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	38.40%	38.90%
Fico Score Greater Than or Equal to 580 and Lower Than 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	30.00%	29.60%
Fico Score Greater than 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	31.60%	31.50%
Loan to Value [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	100.00%	100.00%
Loan to Value Ratio Lower than 100 [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	21.70%	21.40%
Loan to Value Ratio Greater than or Equal to 100 and Lower than 120 [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	47.70%	47.70%
Loan to Value Ratio Greater than 120 [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of Accounts Receivable by Quality Indicator	30.60%	30.90%