Other Retirement Plans (Schedule of Covered Employees and Contributions, Multi-Employer Plans) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) employee	Sep. 30, 2014 USD ($) employee	Sep. 30, 2015 USD ($) employee	Sep. 30, 2014 USD ($) employee
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	$ 9.6	$ 12.7	$ 26.6	$ 29.8
Multi-Employer Plans, Pension [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	7.4	11.6	20.0	27.3
Multi-Employer Plans, Postretirement Benefit [Member]
Covered Employees and Contributions, Multi-Employer Plans [Line Items]
Multi-employer plans, contributions (in dollars)	$ 2.2	$ 1.1	$ 6.6	$ 2.5
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	1,689	2,029	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