Shareholders' Equity - Issued and Outstanding Preferred Stock (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Carrying Value	$ 1,250,000	$ 1,231,500
Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred stock, Shares Issued		230,000
Preferred stock, Shares Outstanding		230,000
Carrying Value		$ 230,000
Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred stock, Shares Issued		151,500
Preferred stock, Shares Outstanding		151,500
Carrying Value		$ 151,500
Series E Fixed-To-Floating Rate Non-Cumulative Perpetual Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred stock, Shares Issued	350,000	350,000
Preferred stock, Shares Outstanding	350,000	350,000
Carrying Value	$ 350,000	$ 350,000
Series F Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred stock, Shares Issued	50,000	50,000
Preferred stock, Shares Outstanding	50,000	50,000
Carrying Value	$ 500,000	$ 500,000
Series G Fixed-Rate Reset Non-cumulative Perpetual Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred stock, Shares Issued	40,000
Preferred stock, Shares Outstanding	40,000
Carrying Value	$ 400,000