CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Intangible assets, accumulated amortization	$ 20,220,000	$ 19,187,000
Preferred shares, par value (in dollars per share)	$ 0.01
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	80,200,000	79,537,000
Common stock, shares outstanding (in shares)	80,200,000	79,537,000
Series B Preferred Stock
Preferred shares, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares, authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	3,450,000	3,450,000
Preferred shares, outstanding (in shares)	3,450,000	3,450,000
Liquidation preference	$ 94,201,000	$ 89,430,000
Series C Preferred Stock
Preferred shares, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares, authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	6,900,000	6,900,000
Preferred shares, outstanding (in shares)	6,900,000	6,900,000
Liquidation preference	$ 188,025,000	$ 178,710,000
Series D Preferred Stock
Preferred shares, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares, authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	5,000,000	5,000,000
Preferred shares, outstanding (in shares)	5,000,000	5,000,000
Liquidation preference	$ 135,743,000	$ 129,297,000