Employee Benefits (Details 5) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Profit sharing and 401(k) contributions for the periods
Profit-sharing contributions	$ 1,613	$ 1,001	$ 965
Retirement plan matching contributions	$ 1,602	$ 1,518	$ 1,319

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration