Guarantees (Details) - Standby Letters Of Credit [Member] - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Standby letters of credit outstanding	$ 27,564	$ 23,603
Maximum [Member]
Loss Contingencies [Line Items]
Standby letters of credit expiration period	1 year

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration