Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	29.80%	15.00%	21.70%	14.70%
Income tax expense	$ 9,404	$ 3,595	$ 19,697	$ 10,233
Change in income tax expense	$ 5,800