Shareholders' Equity - Summary of Perpetual Preferred Stock Issued and Outstanding (Parenthetical) (Detail)	Sep. 30, 2020 $ / shares
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	$ 0.01
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series D Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series F Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series J Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series K Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series M Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series N Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series O Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series P Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series Q Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series R Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	0.01
Series S Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock	$ 0.01