Shareholders' Equity - Summary of Preferred Stock Dividends and Distributions (Detail) - $ / shares							3 Months Ended
	Apr. 27, 2021	Feb. 23, 2021	Dec. 17, 2020	Sep. 17, 2020	Jun. 09, 2020	Feb. 18, 2020	Mar. 31, 2021	Mar. 31, 2020
Dividends Payable [Line Items]
Preferred dividends declared, per share							$ 0.4375	$ 0.4375
Series A Preferred Shares [Member]
Dividends Payable [Line Items]
Dividends Payable Date Declared Day Month And Year		Feb. 28, 2023	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2009	Feb. 28, 2018
Dividends Payable Date Of Record Day Month And Year		Mar. 31, 2031	Dec. 31, 2031	Sep. 30, 2030	Jun. 30, 2030	Mar. 31, 2031
Dividend Payable Date To Be Paid Day Month And Year		Apr. 30, 2015	Jan. 15, 2021	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015
Preferred dividends declared, per share		$ 0.43750	$ 0.43750	$ 0.43750	$ 0.43750	$ 0.43750
Series A Preferred Shares [Member] | Subsequent Event [Member]
Dividends Payable [Line Items]
Dividends Payable Date Declared Day Month And Year	Apr. 30, 2027
Dividends Payable Date Of Record Day Month And Year	Jun. 30, 2030
Dividend Payable Date To Be Paid Day Month And Year	Jul. 31, 2015
Preferred dividends declared, per share	$ 0.43750