Retirement Plans (Schedule of Costs of Retirement Plans) (Details) - Salaried Benefit Plan - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 562	$ 672	$ 1,187	$ 1,473
United States
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	410	445	861	1,137
Canada
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	54	67	113	118
United Kingdom
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 98	$ 160	$ 213	$ 218