Shareholders' Equity (Detail)							3 Months Ended		9 Months Ended
	Sep. 15, 2021 USD ($)	Aug. 06, 2021 $ / shares	Sep. 15, 2020 USD ($)	Sep. 11, 2020 USD ($)	Aug. 07, 2020 $ / shares	May 07, 2020 $ / shares	Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2020 $ / shares	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2020 $ / shares	May 06, 2021	Dec. 31, 2020 $ / shares	May 03, 2016 USD ($)
Class of Stock [Line Items]
Cash dividend declared - common shares (in dollars per share)		$ 0.31				$ 0.31	$ 0.31	$ 0.31	$ 0.93	$ 0.93
Payments of dividends | $	$ 10,800,000			$ 10,900,000
Preferred shares par value (in dollars per share)							1.00		1.00			$ 1.00
Liquidation preference (in dollars per share)							$ 25,000		$ 25,000			$ 25,000
Depositary shares, dividends per share (in dollars per share)		0.437500			$ 0.330556
Number of shares repurchased (in shares) | shares									0
Fractional interest per one preference share											0.001
Series A Preferred Stock
Class of Stock [Line Items]
Payments of dividends | $	$ 2,600,000		$ 2,000,000
Preferred stock, dividends declared (in dollars per share)		$ 437.500			$ 330.556
Preferred stock, dividend rate (in percentage)		7.00%			7.00%
Preferred shares par value (in dollars per share)		$ 1.00			$ 1.00
Liquidation preference (in dollars per share)		$ 25,000			$ 25,000
2016 Repurchase Authorization
Class of Stock [Line Items]
Total number of shares authorized for purchase | $													$ 150,000,000
Remaining number of shares available under repurchase authorization | $							$ 53,300,000		$ 53,300,000