Shareholders' Equity And Earnings Per Share (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2019	Dec. 19, 2008	Apr. 30, 2019	Jan. 31, 2019	Jun. 30, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Temporary Equity [Line Items]
Cash dividends declared per common share (usd per share)	$ 0.25		$ 0.25	$ 0.25		$ 0.25	$ 0.19	$ 0.75	$ 0.57
Common stock dividends per share declared annualized (usd per share)	$ 1.00		$ 1.00	$ 1.00
US Treasury
Temporary Equity [Line Items]
Warrants outstanding, shares		1,643,295
Warrant termination period		10 years
Warrants exercised, shares										22,952
Common stock shares issued from exercise of warrants										16,571
Series D Preferred Stock
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	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%
London Interbank Offered Rate (LIBOR) | Series D Preferred Stock
Temporary Equity [Line Items]
Preferred stock, dividend rate, percentage, variable spread					4.06%