Shareholders' Equity (Narrative) (Details) $ / shares in Units, $ in Millions				12 Months Ended
	Jan. 15, 2021 $ / shares	Nov. 25, 2020	Jan. 12, 2018 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 18, 2018 USD ($) $ / shares shares
Class Of Stock [Line Items]
Preferred stock, shares authorized | shares				12,500,000
Common stock repurchase, authorized | $							$ 30.0
Common stock repurchase, shares | shares						117,000
Common stock repurchase, weighted average price per share | $ / shares						$ 19.91
Additional number of common stock shares repurchased | shares					311,000		428,000
Additional common stock repurchased, weighted average price per share | $ / shares					$ 22.03		$ 21.45
Stock price as percentage of market value				100.00%
Remaining shares authorized under DRIP | shares				427,000
Accrued preferred stock dividends | $				$ 1.2	$ 1.2
Subsequent Event [Member]
Class Of Stock [Line Items]
Dividends payable, date declared	Jan. 15, 2021
Common stock, dividends declared | $ / shares	$ 0.066
Dividends payable, date to be paid	Feb. 22, 2021
Dividends payable, date of record	Feb. 10, 2021
Common Stock [Member]
Class Of Stock [Line Items]
Stockholders' equity, reverse stock split, conversion ratio		0.15
Stockholders' equity, reverse stock split				Each 6.6 shares of the Company's issued and outstanding common stock were combined into one share of the Company's common stock.
Series B [Member]
Class Of Stock [Line Items]
Dividend rate percentage				7.25%	7.25%	7.25%
Redemption date				May 22, 2017
Redemption price per share | $ / shares			$ 25.00	$ 25.00
Preferred stock, shares authorized | shares				1,450,000	1,450,000
Preferred stock redeemed, shares | shares			2,000,000
Redemption price plus accrued and unpaid dividends amount | $			$ 50.0
Series B [Member] | Subsequent Event [Member]
Class Of Stock [Line Items]
Preferred stock dividends declared | $ / shares	$ 0.453125
Series C [Member]
Class Of Stock [Line Items]
Dividend rate percentage				6.50%	6.50%	6.50%
Redemption date				Aug. 24, 2022
Redemption price per share | $ / shares				$ 25.00
Preferred stock, shares authorized | shares				6,450,000	6,450,000
Series C [Member] | Subsequent Event [Member]
Class Of Stock [Line Items]
Preferred stock dividends declared | $ / shares	$ 0.406250