Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Contingency [Line Items]
Income tax expense (benefit)	$ 32,816		$ (9,905)	$ 89,518	$ (61,519)
Effective Income Tax Rate Reconciliation, Percent	28.00%		24.90%	28.40%	31.90%
U.S federal statutory rate, percent				21.00%	35.00%
Write-off of unrealized deferred tax asset	$ 1,000			$ 3,000	$ 2,000
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		$ 256,000