Taxes (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Oct. 02, 2016	Oct. 01, 2016
Operating Loss Carryforwards [Line Items]
Cancellation of debt income						$ 3,414,000,000
Decrease in operating loss carryforwards							$ 3,185,000,000
Operating loss carryforwards	$ 980,200,000	$ 980,200,000
Annual limitation on operating loss use	29,800,000.0	29,800,000.0
Tax credit carryforwards	23,900,000	23,900,000
Increase (decrease) in valuation allowance		35,700,000	$ (1,289,000,000)	$ 865,100,000
Tax loss carryforwards	$ 271,405,000	271,405,000	376,293,000	1,135,000,000
Additional valuation allowance			1,185,000,000
Net deferred tax assets			1,022,000,000
Tax Cuts and Jobs Act of 2017, Income tax expense (benefit)		330,900,000
Repatriation of foreign earnings		1,500,000
Cumulative foreign earnings		$ 4,200,000
Sequestration reduction rate	6.60%	6.60%
Tax Cuts and Jobs Act of 2017, Income tax expense (benefit) related to valuation allowance	$ (22,400,000)
Tax Cuts and Jobs Act of 2017, Provisional income tax expense (benefit) related to change in limit on deductible for covered employees		$ 200,000
Estimated sequestration reduction	1,500,000
Valuation allowance	610,500,000	610,500,000
Reductions as a result of lapses in the statute of limitations		0	37,110,000	$ 37,100,000
Interest and penalties accrued related to unrecognized tax benefits	$ 600,000	$ 600,000	$ 500,000
Scenario, forecast
Operating Loss Carryforwards [Line Items]
Gross unrecognized tax benefits					$ 3,300,000
Alternative minimum tax credits
Operating Loss Carryforwards [Line Items]
Decrease in tax credit carryforwards							$ 76,000,000
Tax credit carryforwards						25,600,000
Capital loss carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards						64,500,000
Domestic tax authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards						$ 957,100,000