Income Taxes (Details 2) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Income Tax Expense (Benefit)			$ 63,851	$ 15,817	$ (151,157)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			35.00%	35.00%	35.00%
Changes in Valuation and Qualifying Accounts
Charges Utilized	$ (21,527)
Tax Valuation Allowance
Changes in Valuation and Qualifying Accounts
Balance at Beginning of Period		$ 50,911	$ 23,529	$ 20,717	$ 193,874
Charged (Credited) to Operations			0	0	0
Charged to Other Account			5,855	2,812	1,299
Charges Utilized			0	0	(174,456)
Balance at End of Period	$ 50,911		50,911	$ 23,529	$ 20,717
2017 U.S.Tax Reform Member [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount			$ 20,700
Scenario, Forecast [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%