Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Income tax benefit on exercise of stock options		$ 335
Capitalized issuance costs	$ 186	$ 260

Amount of deferred tax expense from write-off of the deferred tax asset related to deductible stock options at exercise.

No definition available.

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