Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Income tax expense (benefit)	$ 56,702	$ (51,614)
Effective Income Tax Rate Reconciliation, Percent	28.70%	33.80%
U.S federal statutory rate, percent	21.00%	35.00%
Write-off of unrealized deferred tax asset	$ 2,000	$ 1,000
Benefit related to certain income tax matters		$ 1,000
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