Finance Receivables (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unused lines of credit, wholesale	$ 955,500,000	$ 909,900,000
Approved but unfunded retail loans	137,700,000	139,300,000
Percent of gross receivables originated in Texas	0.00%	0.00%
Lower of cost or market adjustment					32,000,000
Receivables past due and accruing interest	28,033,000	28,378,000	35,742,000	26,790,000	24,953,000
Level at which FICO score is considered prime	640
Non-accrual status wholesale finance receivables	$ 0	$ 0