Discontinued Operations (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2019	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase (decrease) in accounts payable and other accrued liabilities	$ 18,400,000		$ 41,900,000	$ (7,800,000)
Disposal Group, Including Discontinued Operation, Revenue				0
Disposal Group, Including Discontinued Operation, Costs of Goods Sold				0
Disposal Group, Including Discontinued Operation, General and Administrative Expense				(200,000)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax				200,000
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax				200,000
Discontinued Operation, Tax Effect of Discontinued Operation				46,000,000
Net income from discontinued operations available for diluted earnings per share	0	$ 38,800,000	0	46,000,000
Gain (Loss) on Disposition of Assets	27,800,000	$ 113,400,000	3,000,000	113,400,000
Cash Provided by (Used in) Operating Activities, Discontinued Operations				(2,800,000)
Proceeds from Sales of Assets, Investing Activities	$ 258,300,000		$ 0	130,100,000
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase (decrease) in accounts payable and other accrued liabilities				(3,000,000)
Gain (Loss) on Disposition of Assets				200,000
Proceeds from Sales of Assets, Investing Activities				200,000
Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of Stock, Consideration Received on Transaction				$ 100,000