Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Preferred stock, par value (in dollars per share)	$ 100	$ 100
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, issued (in shares)	167,099,432	167,099,432
Common stock, outstanding (in shares)	105,653,644	106,212,908
Treasury stock, shares (in shares)	61,445,788	60,886,524