Income Taxes (Summary Of Tax Loss And Tax Credit Carryforwards) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Tax Credit Carryforward [Line Items]
Deferred tax asset on tax carryforwards	$ 101,300	$ 105,600
Valuation Allowance, Amount	(148,200)	$ (145,900)
Tax Loss and Credit Carryforwards [Member]
Tax Credit Carryforward [Line Items]
Deferred tax asset on tax carryforwards	101,300
Valuation Allowance, Amount	(96,500)
Net deferred tax asset on tax carryforwards	4,800
U.S. Federal Tax Credits [Member]
Tax Credit Carryforward [Line Items]
2016-2020	18,500
After 2020	1,500
Indefinite	0
Total tax carryforwards	20,000
Deferred tax asset on tax carryforwards	20,000
Valuation Allowance, Amount	(20,000)
Net deferred tax asset on tax carryforwards	0
U.S Federal Tax Losses [Member]
Tax Credit Carryforward [Line Items]
2016-2020	200
After 2020	1,000
Total tax carryforwards	1,200
Deferred tax asset on tax carryforwards	500
Valuation Allowance, Amount	(400)
Net deferred tax asset on tax carryforwards	100
U.S. State Tax Credits [Member]
Tax Credit Carryforward [Line Items]
2016-2020	4,000
After 2020	2,000
Indefinite	20,000
Total tax carryforwards	26,000
Deferred tax asset on tax carryforwards	17,000
Valuation Allowance, Amount	(16,300)
Net deferred tax asset on tax carryforwards	700
U.S. State Tax Losses [Member]
Tax Credit Carryforward [Line Items]
2016-2020	33,500
After 2020	824,500
Total tax carryforwards	858,000
Deferred tax asset on tax carryforwards	38,100
Valuation Allowance, Amount	(37,500)
Net deferred tax asset on tax carryforwards	600
Non-U.S. Tax Losses [Member]
Tax Credit Carryforward [Line Items]
2016-2020	49,800
After 2020	9,200
Indefinite	89,900
Total tax carryforwards	148,900
Deferred tax asset on tax carryforwards	25,700
Valuation Allowance, Amount	(22,300)
Net deferred tax asset on tax carryforwards	$ 3,400