Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Contingency [Line Items]
Income tax (benefit) expense	$ (22,422)		$ (20,087)	$ 67,096	$ (81,606)
Effective Income Tax Rate Reconciliation, Percent	(70.80%)		51.80%	19.30%	35.30%
U.S federal statutory rate, percent	21.00%			21.00%	35.00%
Income tax benefit related to federal and state income tax filings for prior year	$ 3,000			$ 3,000
Charge related to certain income tax matters			$ 1,000		$ 1,000
Write-off of unrealized deferred tax asset				3,000	1,000
Benefit Related to Refund of Interest Paid on Tax Assessments					$ 3,000
Domestic Tax Authority
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax Benefit	$ 24,000	$ 256,000		$ 24,000