|
Long-term Incentive Compensation Plans (Details) (USD $)
Share data in Millions, unless otherwise specified |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2015
|
Mar. 31, 2014
|
|
| Long-term Incentive Compensation Plans [Abstract] | ||
| Holding units purchased in period (in units) | 0.7 | 0.2 |
| Dollar amount paid for holding units acquired | $ 17,000,000 | $ 3,700,000 |
| Open-market purchases of holding units (in units) | 0.6 | |
| Dollar amount paid for open-market purchases of holding units | 15,100,000 | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Units issued upon options exercised (in units) | 0.2 | |
| Proceeds from stock options exercised | $ 3,901,000 | $ 4,656,000 |
| Employees and Eligible Directors [Member] | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Restricted holding unit awards to employees (in units) | 0.1 | 0.2 |