CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Preferred stock, par value per share (in dollars per share)	$ 5.00	$ 5.00
Preferred stock, shares authorized (in shares)	2,000,000	2,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, shares (in shares)	8,394,022	8,408,770
Common Class A [Member]
Common stock, par value per share (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	39,112,722	39,098,792
Common Class B [Member]
Common stock, par value per share (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	1,617,998	1,617,998
Common stock, shares outstanding (in shares)	1,617,998	1,617,998