Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	140,364,000	140,364,000
Common stock, shares issued	43,023,000	41,920,000
Common stock, shares outstanding	43,023,000	41,920,000
Excess stock, par value	$ 0.10	$ 0.10
Excess stock, shares authorized	3,000,000	3,000,000
Excess stock, shares issued	0	0
Excess stock, shares outstanding	0	0
Series C Preferred Stock [Member]
Cumulative redeemable preferred stock, percentage	6.75%	6.75%
Cumulative redeemable preferred stock, par value	$ 0.10	$ 0.10
Cumulative redeemable preferred stock, shares authorized	13,750,000	13,750,000
Cumulative redeemable preferred stock, shares issued	9,884,000	9,884,000
Cumulative redeemable preferred stock, shares outstanding	9,884,000	9,884,000
Series D Preferred Stock [Member]
Cumulative redeemable preferred stock, percentage	6.375%	6.375%
Cumulative redeemable preferred stock, par value	$ 0.10	$ 0.10
Cumulative redeemable preferred stock, shares authorized	9,300,000	9,300,000
Cumulative redeemable preferred stock, shares issued	7,698,000	6,434,000
Cumulative redeemable preferred stock, shares outstanding	7,698,000	6,434,000