Adoption Of Accounting Standards Update No. 2016-09, Improvements To Employee Share Based Payment Accounting (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 19,264,000		$ 19,611,000
Common stock	34,521,000		34,080,000
Deferred tax assets	5,961,000		$ 5,742,000
Excess tax benefit from the exercise of stock options	$ 35,000	$ 208,000