Employee Benefit Plans (Textuals) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Percentage of medical coverage cost payable by participants	100.00%
Amendments		$ 3.2
Decrease in projected benefit obligation		50.6
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amendments	$ 0.0	$ 0.1
Estimated prior service (cost) credits	0.1
Estimated actuarial gains (losses)	$ 9.3
Long-term rate of return on assets assumption (as a percent)	7.50%	7.50%	7.50%
Discount rate (as a percent)	3.66%	4.17%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amendments	$ 0.0	$ 0.0
Estimated prior service (cost) credits	(1.4)
Estimated actuarial gains (losses)	$ 1.3
Long-term rate of return on assets assumption (as a percent)	0.00%	0.00%	0.00%
Discount rate (as a percent)	3.25%	3.50%
Fixed Income, Money Market, Cash and Guaranteed Investment Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Target (as a percent)	75.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target (as a percent)	25.00%
International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target (as a percent)	12.50%
U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target (as a percent)	12.50%
UNITED KINGDOM
Defined Benefit Plan Disclosure [Line Items]
Components of fair value in our plan assets	7.00%
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation (as a percent)	88.00%
Plan assets (as a percent)	87.00%
Long-term rate of return on assets assumption (as a percent)	7.50%
Components of fair value in our plan assets	87.00%
Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Components of fair value in our plan assets	6.00%