Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ / shares in Thousands, $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Accounts receivable, allowance for credit losses	$ 15	$ 16
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, shares authorized (in shares)	200,000,000
Common Stock (No Par Value) [Member]
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)	105,036,512	104,286,324
Common stock, shares outstanding (in shares)	88,117,327	87,539,056
Treasury stock (in shares)	16,919,185	16,747,268
Class A Common Stock (No Par Value) [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)	9,675,139	9,424,691
Common stock, shares outstanding (in shares)	7,573,222	7,426,512
Treasury stock (in shares)	2,101,917	1,998,179