Other Retirement Plans (Schedule of Covered Employees and Contributions, Multi-Employer Plans) (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) employee	Jun. 30, 2014 USD ($) employee	Jun. 30, 2015 USD ($) employee	Jun. 30, 2014 USD ($) employee
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	$ 11.5	$ 8.8	$ 17.1	$ 17.1
Multi-Employer Plans, Pension [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	9.3	8.0	12.7	15.8
Multi-Employer Plans, Postretirement Benefit [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	$ 2.2	$ 0.8	$ 4.4	$ 1.3
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	1,124	1,308	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	2,463	2,167	2,463	2,167