Investments in Affiliates (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 390.3	$ 346.3	$ 398.0
Equity in net earnings of affiliates	53.5	48.9	49.7
Equity Method Investment, Summarized Financial Information [Abstract]
Total assets	8,474.8	7,738.4
Total liabilities	7,751.6	7,080.8
Partners’ equity	723.2	657.6
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenues	377.8	364.2	352.9
Costs	226.5	220.5	212.2
Income before income taxes	151.3	143.7	140.7
Receivables from affiliates	41.5	122.9	106.3
Retained Earnings, Undistributed Earnings from Equity Method Investees	246.0	208.2
Retail Finance Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	354.4	322.2
Equity in net earnings of affiliates	48.6	43.6	43.4
Manufacturing Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	20.7	14.3
Other Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	15.2	9.8
Manufacturing and Other Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Equity in net earnings of affiliates	$ 4.9	$ 5.3	$ 6.3