Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
(Benefit) provision for income taxes	$ 12,393		$ 23,000	$ 31,309	$ 22,972
Effective income tax rate	18.50%		5.90%	18.40%	5.00%
Discrete tax provision	$ (51,100)			$ (51,200)
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