Treasury Stock (Details) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Treasury Stock (Textual)
Number of repurchase of shares authorized by board of directors			$ 20,000,000
Remaining authorized repurchase amount	$ 17,558,000	$ 19,049,000
Treasury stock purchased (in shares)	234	152	2,030
Cash consideration paid for repurchase of common stock	$ 1,492,000	$ 951,000	$ 14,930,000
Commissions paid to brokers	$ 9,000	$ 6,000
Weighted average price per share of stock repurchase (in usd per share)	$ 6.35	$ 6.27