Income Taxes (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Income Taxes
Federal statutory tax rate			21.00%		35.00%
Income tax provision	$ 508	$ 1,014	$ 7,036	$ (1,586)
Transition tax benefit	$ 1,400		$ 1,400
Decrease in effective tax rate (as a percent)	15.2		3.1
Tax benefit recognized upon the expiration of statute of limitation			$ 300
Interest and penalties previously accrued credited to interest expenses	$ 200		$ 200
Deferred tax assets valuation allowance					$ 90,300