Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Current tax expense (benefit):
Income tax provision	$ 11,390	$ 12,127	$ 26,810	$ 25,120
Current income tax expense (benefit)			$ 44,700
Effective tax rate	13.70%	19.10%	19.50%	21.10%
Deferred tax expense (benefit):
Deferred income taxes			$ 3,189	$ (150)
Deferred Income Tax Expense (Benefit), Excluding Discontinued Operations			$ 63,300
Effective tax rate	13.70%	19.10%	19.50%	21.10%