Subsequent Events - Additional Information (Detail) - $ / shares	Aug. 30, 2019	Jul. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Preferred stock, par value			$ 1.00	$ 1.00
Scenario, Forecast [Member]
Subsequent Event [Line Items]
Preferred stock, liquidation preference per share	$ 1,000
Series G Perpetual Fixed-Rate Reset Non-cumulative Preferred Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Preferred stock, shares issued		40,000
Preferred stock, par value		$ 1.00
Preferred stock, liquidation preference per share		$ 10,000
Preferred stock dividend rate		5.00%
Date of change in the dividend rate		Jul. 31, 2024
Dividend payment terms		five-year
U S treasury rate plus additional rate		3.174%
Preferred shares redemption date		Aug. 01, 2024
Preferred stock, redemption feature, redemption term		90 days
Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member] | Scenario, Forecast [Member]
Subsequent Event [Line Items]
Shares expects to redeem	230,000
Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member] | Scenario, Forecast [Member]
Subsequent Event [Line Items]
Shares expects to redeem	151,500