Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 300		$ (918)	$ 427	$ (1,389)
Effective tax rate	19.90%		(20.20%)	20.50%	(21.50%)
Tax cuts and jobs act of 2017, incomplete accounting, transition tax for accumulated foreign earnings, provisional Income tax expense		$ 17,400
Forecast
Income Tax Contingency [Line Items]
Net GILI inclusion income - tax expense						$ 1,600
Foreign tax credits - income tax benefit						$ 1,600