Acquisitions (Details) (USD $) In Millions, unless otherwise specified | 9 Months Ended | |
|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | |
| Acquisitions [Abstract] | ||
| Payments to acquire retail franchises and related assets, net of cash acquired | $ 64.2 | $ 73.1 |
| Number of automobile franchises acquired | 1 | 5 |