Stockholders' Equity-Number of Shares (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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	37,444	37,550	37,444	37,550
Effect of using weighted average common shares outstanding	(7)	(93)	(54)	(180)
Shares used in computing earnings per share - basic	37,437	37,457	37,390	37,370
Effect of shares issuable under stock option plans based on the treasury stock method	351	289	336	260
Effect of contingently issuable restricted shares	123	171	144	131
Shares used in computing earnings per share - diluted	37,911	37,917	37,870	37,761