Stockholders' Equity - Number of Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
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	36,450	36,891
Effect of using weighted average common shares outstanding	224	32
Shares used in computing earnings per share-basic	36,674	36,923
Effect of shares issuable under stock option plans based on the treasury stock method	148	230
Effect of restricted and contingently issuable shares	83	81
Shares used in computing earnings per share-diluted	36,905	37,234