Stockholders' Equity-Number of Shares (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 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	37,230	37,486	37,230	37,486
Effect of using weighted average common shares outstanding	130	66	150	(55)
Shares used in computing earnings per share - basic	37,360	37,552	37,380	37,431
Effect of shares issuable under stock option plans based on the treasury stock method	319	277	331	266
Effect of contingently issuable restricted shares	142	178	143	147
Shares used in computing earnings per share - diluted	37,821	38,007	37,854	37,844