Commitments and Contingencies (Schedule of Other Commitments) (Details) $ in Thousands	1 Months Ended	3 Months Ended				6 Months Ended	12 Months Ended													19 Months Ended	21 Months Ended
	Jan. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2019	Jun. 30, 2018 USD ($)	Mar. 31, 2018	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 30, 2018	Dec. 31, 2017	Nov. 30, 2017	Dec. 31, 2016	Nov. 30, 2016	Dec. 31, 2015	Nov. 30, 2015	Dec. 31, 2014	Nov. 30, 2014	Dec. 31, 2013	Nov. 30, 2013	Nov. 30, 2012	Dec. 31, 2012
Third Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate																	17.37%
Fourth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate															0.00%
Antidumping Duties [Member] | Other Current Assets [Member]
Loss Contingencies [Line Items]
Contingent Receivable		$ 500				$ 500
Antidumping Duties [Member] | Other Assets [Member]
Loss Contingencies [Line Items]
Contingent Receivable		1,300				1,300
Antidumping Duties [Member] | Other Noncurrent Liabilities [Member]
Loss Contingencies [Line Items]
Contingent Liability		10,300				10,300
Antidumping Duties [Member] | First Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate				0.73%	5.92%															0.73%
Contingent Liability								$ 800
Contingent Receivable		$ 1,300				$ 1,300		$ 1,300
Antidumping Duties [Member] | Second Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate																			3.30%
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate		3.92%				13.74%													3.92%
Contingent Liability		$ 4,100				$ 4,100
Decrease in contingent liability		3,900
Antidumping Duties [Member] | Third Annual Review [Member]
Loss Contingencies [Line Items]
Contingent Liability		4,700				4,700
Antidumping Duties [Member] | Fourth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate															0.00%
Antidumping Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate													0.00%
Antidumping Duties [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Contingent Liability		1,500				1,500	$ 800
Contingent Receivable		500				$ 500
Antidumping Duties [Member] | Seventh Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate									0.00%
Loss Contingency Preliminary Purchase Price Of Anti dumping Duty Rate	0.0
Antidumping Duties [Member] | Minimum [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate			0.00%				0.00%
Antidumping Duties [Member] | Maximum [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate			42.57%			42.57%
Countervailing Duties [Member] | Other Current Assets [Member]
Loss Contingencies [Line Items]
Contingent Receivable		100				$ 100
Countervailing Duties [Member] | Other Assets [Member]
Loss Contingencies [Line Items]
Contingent Receivable		300				300
Countervailing Duties [Member] | Other Current Liabilities [Member]
Loss Contingencies [Line Items]
Contingent Liability		40				40
Countervailing Duties [Member] | First and Second Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate																					1.50%
Contingent Receivable		200				200
Countervailing Duties [Member] | Third Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate																		1.50%
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate																		1.38%
Contingent Receivable		50				50
Countervailing Duties [Member] | Fourth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate																1.06%
Contingent Receivable		20				20
Countervailing Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Contingent Receivable		80				80
Countervailing Duties [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Contingent Liability		$ 40				$ 40	$ 400
Countervailing Duties [Member] | Seventh Annual Review [Member]
Loss Contingencies [Line Items]
Contingent Liability	$ 2,000
Loss Contingency Preliminary Purchase Price Of Countervailing Duty Rate	24.61
Countervailing Duties [Member] | Eighth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate								1.06%
Countervailing Duties [Member] | Minimum [Member] | First and Second Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate																					0.83%
Countervailing Duties [Member] | Minimum [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate				0.11%
Countervailing Duties [Member] | Minimum [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate			2.96%
Countervailing Duties [Member] | Maximum [Member] | First and Second Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate																					0.99%
Countervailing Duties [Member] | Maximum [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate				0.85%
Countervailing Duties [Member] | Maximum [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate			3.10%
Deposit One [Member] | Antidumping Duties [Member] | First Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate																				6.78%
Deposit One [Member] | Antidumping Duties [Member] | Third Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate																	3.30%
Deposit One [Member] | Antidumping Duties [Member] | Fourth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate															5.92%
Deposit One [Member] | Antidumping Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate													5.92%
Deposit One [Member] | Antidumping Duties [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate											17.37%
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate											42.57%
Deposit One [Member] | Countervailing Duties [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate																1.50%
Deposit One [Member] | Countervailing Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate														0.83%
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate														0.11%
Contingent Receivable				$ 70
Deposit One [Member] | Countervailing Duties [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate												0.99%
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate												3.10%
Deposit One [Member] | Countervailing Duties [Member] | Seventh Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate										1.38%
Deposit Two [Member] | Antidumping Duties [Member] | First Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate																				3.30%
Deposit Two [Member] | Antidumping Duties [Member] | Third Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate																	5.92%
Deposit Two [Member] | Antidumping Duties [Member] | Fourth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate															13.74%
Deposit Two [Member] | Antidumping Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate													13.74%
Deposit Two [Member] | Antidumping Duties [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate											0.00%
Loss Contingency Modified Purchase Price Of Antidumping Duty Rate											0.00%
Deposit Two [Member] | Countervailing Duties [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate																0.83%
Deposit Two [Member] | Countervailing Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate														0.99%
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate														0.85%
Deposit Two [Member] | Countervailing Duties [Member] | Sixth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate												1.38%
Loss Contingency Modified Purchase Price Of Countervailing Duties Rate												2.96%
Deposit Two [Member] | Countervailing Duties [Member] | Seventh Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Countervailing Duties Rate										1.06%
Deposit Three [Member] | Antidumping Duties [Member] | Fifth Annual Review [Member]
Loss Contingencies [Line Items]
Loss Contingency Purchase Price Of Antidumping Duty Rate													17.37%