Income Taxes - Additional Information (Details) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes [Line Items]
Effective income tax rate reconciliation, percent		22.90%	34.50%	24.00%	35.60%
Unrecognized tax benefits		$ 100,000		$ 100,000
Unrecognized tax benefits that would impact effective tax rate		0		$ 0
Federal corporate income tax rate				21.00%		35.00%
Tax Cuts and Jobs Act of 2017 accounting complete				true
Increase in deferred tax provision for income taxes, including adjustments to valuation allowances				$ 1,300,000
Additional income taxes for remaining undistributed foreign earnings not subject to transition tax		0		0
Increase in valuation allowance	$ 2,200,000
Increase in cumulative foreign tax credit carry forward	$ 2,200,000
Increase (decrease) in provision for income tax		$ (1,100,000)
Global Intangible Low-Tax Income
Income Taxes [Line Items]
Current provision for global intangible low-tax income				$ 0
Internal Revenue Service (IRS) | Earliest Tax Year
Income Taxes [Line Items]
Open tax year				2015
Internal Revenue Service (IRS) | Latest Tax Year
Income Taxes [Line Items]
Open tax year				2017
State Local and Foreign Jurisdictions | Earliest Tax Year
Income Taxes [Line Items]
Open tax year				2014
State Local and Foreign Jurisdictions | Latest Tax Year
Income Taxes [Line Items]
Open tax year				2017