Stockholders' Equity-Number of Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
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	37,226	37,392
Effect of using weighted average common shares outstanding	(1)	(48)
Shares used in computing earnings per share - basic	37,225	37,344
Effect of shares issuable under stock option plans based on the treasury stock method	335	321
Effect of restricted and contingently issuable shares	164	165
Shares used in computing earnings per share - diluted	37,724	37,830