Income Tax Matters Income Tax Matters Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Operating Loss Carryforwards	$ 275,100,000	$ 275,100,000
Tax Credit Carryforward, Amount	23,300,000	23,300,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		(2,700,000)	$ (5,500,000)	$ 2,000,000
Unrecognized Tax Benefits	1,500,000	1,500,000	1,800,000	1,700,000	$ 2,200,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	400,000	400,000	700,000	600,000
Accrued interest and penalties on unrecognized tax benefits	100,000	100,000	200,000
Accrued interest and penalties on unrecognized tax benefits, current	0	0
(Decrease) increase in interest and penalty	(100,000)	(100,000)	$ 0	(1,200,000)
Foreign currency impact on gross unrecognized tax benefit (including interest and penalties) which increased (decreased) Other comprehensive income (loss)				$ 100,000
Provisional decrease in deferred tax assets	29,000,000
Provisional Transition Tax obligation	3,700,000
Accrued witholding taxes due to Canadian earnings deemed no longer permanently reinvested	2,200,000	2,200,000
Provisional Section 162(m) obligation	$ 2,300,000	$ 2,300,000