Other Retirement Plans (Schedule of Covered Employees and Contributions, Multi-Employer Plans) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2015 USD ($) employee	Mar. 31, 2014 USD ($) employee
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	$ 5.6	$ 8.3
Multi-Employer Plans, Pension [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	3.4	7.8
Multi-Employer Plans, Postretirement Benefit [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	$ 2.2	$ 0.5
Workforce Subject to Collective Bargaining Arrangements [Member] | Unionized Employees [Member] | Low [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, covered employees (in number of employees) | employee	590	1,098
Workforce Subject to Collective Bargaining Arrangements [Member] | Unionized Employees [Member] | High [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, covered employees (in number of employees) | employee	1,124	1,308