Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
(Benefit) provision for income taxes	$ (18,916)	$ 28
Effective income tax rate	18.23%	(0.04%)
Discrete tax provision	$ (51,100)
Income tax provision, remeasurement of deferred taxes			$ 126,500
Income tax provision, adjustment to AMT credit	$ 300
Alternative Minimum Tax Credit
Operating Loss Carryforwards [Line Items]
Provisional income tax benefit			$ 4,900