Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Contingency [Line Items]
Income tax (benefit) expense	$ (5,973,000)	$ 2,022,000	$ (6,898,000)	$ 11,596,000
Additional income tax expense resulted from adjustments		$ 8,900,000		18,600,000
Tax expense (benefit) from exercise of stock option awards			1,200,000	200,000
Income tax interest and penalties			0	$ 33,000
Decision To Elect Bonus Depreciation In Prior Year [Member]
Income Tax Contingency [Line Items]
Income tax (benefit) expense			(900,000)
Increase In Valuation Allowance On Deferred Tax Assets [Member]
Income Tax Contingency [Line Items]
Income tax (benefit) expense			9,400,000
Partial Valuation Allowance Against Canadian Deferred Tax Assets [Member]
Income Tax Contingency [Line Items]
Income tax (benefit) expense			1,400,000
Reduction In Foreign Tax Expense [Member]
Income Tax Contingency [Line Items]
Income tax (benefit) expense			$ (1,100,000)