Other Employee Benefit Programs Defined Contribution Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 11,231	$ 9,521	$ 9,532
Domestic Plan [Member] | G&W 401k savings plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%
Foreign Plan [Member] | Canadian Retirement Benefit Plan 1 [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Foreign Plan [Member] | Canadian Retirement Benefit Plan 2 [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	5.00%
Foreign Plan [Member] | Australian Retirement Benefit Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	9.50%	9.50%	9.50%