6. Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings per share:
Weighted average number of common shares outstanding during the period used to compute basic earnings per share	21,178	23,076	21,375	23,296
Incremental common shares attibutable to exercise of outstanding options and warrants	3,945	4,526	4,018	4,728
Weighted average number of common shares used to compute diluted earnings per share	25,123	27,602	25,393	28,024