Shareholders' Equity And Earnings Per Share (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended		6 Months Ended
	May 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Jun. 30, 2015	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Temporary Equity [Line Items]
Preferred stock, shares issued (in shares)					5,000,000	5,000,000	5,000,000	5,000,000	5,000,000
Preferred stock, liquidation value per share (usd per share)					$ 25	$ 25	$ 25	$ 25	$ 25
Cash dividends declared per common share (usd per share)		$ 0.28	$ 0.28		$ 0.28	$ 0.25	$ 0.56	$ 0.50
Common stock dividends per share declared annualized (usd per share)		$ 1.12	$ 1.12
Series D Preferred Stock
Temporary Equity [Line Items]
Sale of Stock, Number of Shares Issued in Transaction				5,000,000
Preferred stock, shares issued (in shares)					5,000,000	5,000,000	5,000,000	5,000,000	5,000,000
Preferred stock, liquidation value per share (usd per share)				$ 25	$ 25	$ 25	$ 25	$ 25	$ 25
Preferred stock, value				$ 125,000	$ 125,000	$ 125,000	$ 125,000	$ 125,000	$ 125,000
Preferred stock, dividend rate, percentage				6.50%
Series E Preferred Stock
Temporary Equity [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	11,500
Preferred stock, shares issued (in shares)					11,500	0	11,500	0	0
Preferred stock, liquidation value per share (usd per share)	$ 25,000				$ 25,000	$ 0	$ 25,000	$ 0	$ 0
Preferred stock, value					$ 287,500	$ 0	$ 287,500	$ 0	$ 0
Preferred stock, dividend rate, percentage	6.875%
Depositary Shares, Series E Preferred Stock
Temporary Equity [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	11,500,000
Sale of Stock, Consideration Received on Transaction	$ 287,500
London Interbank Offered Rate (LIBOR) | Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, dividend rate, percentage, variable spread				4.06%