Shareholders' Equity (Detail) $ / shares in Units, $ in Millions					3 Months Ended		9 Months Ended
	Sep. 15, 2022 USD ($)	Aug. 04, 2022 $ / shares	Sep. 15, 2021 USD ($)	Aug. 06, 2021 $ / shares	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 $ / shares	Sep. 30, 2022 USD ($) $ / shares shares	Sep. 30, 2021 $ / shares shares	Aug. 05, 2022	Dec. 31, 2021 $ / shares	May 03, 2016 USD ($)
Class of Stock [Line Items]
Dividend declared per common share (in dollars per share)		$ 0.31		$ 0.31	$ 0.31	$ 0.31	$ 0.93	$ 0.93
Payments of dividends | $	$ (11.2)		$ (10.8)
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
Fractional interest per one preference share				0.001					0.001
Depositary shares, dividends per share (in dollars per share)		0.43750		$ 0.43750
Number of shares repurchased (in shares) | shares							0	0
Series A Preferred Stock
Class of Stock [Line Items]
Payments of dividends | $	$ (2.6)		$ (2.6)
Preferred stock, dividends declared (in dollars per share)		$ 437.50		$ 437.50
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 | $											$ 150.0
Remaining number of shares available under repurchase authorization | $					$ 53.3		$ 53.3