Stockholders' Equity - Number of Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
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	36,255	36,450
Effect of using weighted average common shares outstanding	31	224
Shares used in computing earnings per share-basic	36,286	36,674
Effect of shares issuable under stock option plans based on the treasury stock method	131	148
Effect of restricted and contingently issuable shares	82	83
Shares used in computing earnings per share-diluted	36,499	36,905