|
Goodwill (Details) (USD $)
In Thousands, unless otherwise specified |
9 Months Ended | 12 Months Ended |
|---|---|---|
|
Sep. 30, 2012
acquisition
|
Dec. 31, 2011
acquisition
reporting_unit
|
|
| Goodwill [Abstract] | ||
| Number of businesses acquired | 0 | 4 |
| Number of reporting units | 3 | |
| Goodwill [Roll Forward] | ||
| Goodwill, beginning balance | $ 256,060 | $ 224,920 |
| Goodwill arising from acquisitions | 31,140 | |
| Other | 23 | |
| Goodwill, ending balance | $ 256,037 | $ 256,060 |