Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ / shares in Thousands, $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Accounts receivable, allowance for credit losses	$ 11	$ 10
Series A Perpetual Preferred Stock, par value (in dollars per share)	$ 0	$ 0
Series A Perpetual Preferred Stock, shares authorized (in shares)	1,500,000	1,500,000
Series A Perpetual Preferred Stock, shares issued (in shares)	650,000	650,000
Series A Perpetual Preferred Stock, shares outstanding (in shares)	650,000	650,000
Series A Perpetual Preferred Stock, liquidation value	$ 650	$ 650
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	103,898,352	103,100,856
Common stock, shares outstanding (in shares)	88,652,172	88,140,259
Treasury stock (in shares)	15,246,180	14,960,597
Common Class A [Member]
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	9,169,198	8,935,773
Common stock, shares outstanding (in shares)	7,171,019	7,048,006
Treasury stock (in shares)	1,998,179	1,887,767

Amount of allowance for credit loss on receivable, classified as other and current.

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Face amount per share of no-par value common stock.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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The aggregate liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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