Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jan. 01, 2017
Income Taxes [Line Items]
U.S. federal statutory corporate pretax rate			35.00%
Deferred Tax Assets, Net	$ 0		$ 0
Tax Adjustments, Settlements, and Unusual Provisions			15,700,000
Tax Adjustments Retained Earnings Effect			0.0
Deferred Tax Assets, Valuation Allowance	(538,520,000)		(538,520,000)		$ (580,100,000)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ (3,253,000)	$ 36,696,000	$ (41,570,000)	$ 240,897,000