XML 156 R136.htm IDEA: XBRL DOCUMENT v3.20.4
Parent Company Condensed Financial Statements (Condensed Balance Sheet - Additional Information) (Details) - $ / shares
Dec. 31, 2020
Dec. 31, 2019
Balance sheets    
Common stock, par value (in dollars per share) $ 0.001 $ 0.001
Common stock, shares authorized (in shares) 200,000,000 200,000,000
Common stock, shares issued (in shares) 167,240,600 166,621,959
Treasury stock, shares (in shares) 25,675,371 20,996,574