Stockholders' Equity-Number of Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
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	37,392	37,307
Effect of using weighted average common shares outstanding	(48)	(26)
Shares used in computing earnings per share - basic	37,344	37,281
Effect of shares issuable under stock option plans based on the treasury stock method	241	233
Effect of contingently issuable restricted shares	145	91
Shares used in computing earnings per share - diluted	37,730	37,605