Retirement and Other Postretirement Benefit Plans - Schedule of Impact of One-Percentage-Point Change in Expected Long-term Rate of Return and Discount Rate on Pension Expense and Retirement Obligation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
U.S. Non-qualified Defined Benefit Retirement Plans
Impact of one-percentage-point increase and a one-percentage-point decrease in the expected long-term rate of return and discount rate on periodic pension expense in next fiscal year
One-percentage-point increase in discount rate	$ (0.2)
One-percentage-point decrease in discount rate	0.4
Impact of one-percentage-point increase and a one-percentage-point decrease in the discount rate on retirement obligation as of December 31, 2014
One-percentage-point increase in discount rate	(1.0)
One-percentage-point decrease in discount rate	1.1
Retiree Medical Plans
Impact of one-percentage-point increase and a one-percentage-point decrease in the discount rate on retirement obligation as of December 31, 2014
One-percentage-point increase in discount rate	(0.4)
One-percentage-point decrease in discount rate	0.4
United Kingdom defined benefit plan (the U.K. Plan)
Impact of one-percentage-point increase and a one-percentage-point decrease in the expected long-term rate of return and discount rate on periodic pension expense in next fiscal year
One-percentage-point increase in expected long-term rate of return	(1.6)
One-percentage-point increase in discount rate	(0.2)
One-percentage-point decrease in expected long-term rate of return	1.6
One-percentage-point decrease in discount rate	0.4
Impact of one-percentage-point increase and a one-percentage-point decrease in the discount rate on retirement obligation as of December 31, 2014
One-percentage-point increase in discount rate	(26.2)
One-percentage-point decrease in discount rate	$ 33.9