Stockholders' Equity-Number of Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of the number of shares outstanding with the number of shares used in computing basic and diluted earnings per share
Common shares outstanding, end of period	37,209	37,427	37,270
Effect of using weighted average common shares outstanding	(126)	(15)	(277)
Shares used in computing earnings per share - basic	37,335	37,442	37,547
Effect of shares issuable under stock option plans based on the treasury stock method	330	266	147
Effect of restricted and contingently issuable shares	146	160	103
Shares used in computing earnings per share - diluted	37,811	37,868	37,797