Investment Securities (Continuous Unrealized Loss Position, Fair Value) (Detail) $ in Thousands	Mar. 31, 2020 USD ($)
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	$ 76,844
Continuous unrealized losses existing for less than 12 months, unrealized losses	(1,738)
Continuous unrealized losses existing for greater than 12 months, fair value	57,687
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(10,331)
Total, fair value	134,531
Total, unrealized losses	(12,069)
U.S. Treasury
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	0
Continuous unrealized losses existing for less than 12 months, unrealized losses	0
Continuous unrealized losses existing for greater than 12 months, fair value	0
Continuous unrealized losses existing for greater than 12 months, unrealized losses	0
Total, fair value	0
Total, unrealized losses	0
U.S. Government agencies
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	0
Continuous unrealized losses existing for less than 12 months, unrealized losses	0
Continuous unrealized losses existing for greater than 12 months, fair value	0
Continuous unrealized losses existing for greater than 12 months, unrealized losses	0
Total, fair value	0
Total, unrealized losses	0
Municipal
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	39,637
Continuous unrealized losses existing for less than 12 months, unrealized losses	(207)
Continuous unrealized losses existing for greater than 12 months, fair value	1,006
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(28)
Total, fair value	40,643
Total, unrealized losses	(235)
Corporate notes, financial issuers
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	35,154
Continuous unrealized losses existing for less than 12 months, unrealized losses	(1,518)
Continuous unrealized losses existing for greater than 12 months, fair value	56,681
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(10,303)
Total, fair value	91,835
Total, unrealized losses	(11,821)
Corporate notes, other
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	0
Continuous unrealized losses existing for less than 12 months, unrealized losses	0
Continuous unrealized losses existing for greater than 12 months, fair value	0
Continuous unrealized losses existing for greater than 12 months, unrealized losses	0
Total, fair value	0
Total, unrealized losses	0
Mortgage-backed securities
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	1,007
Continuous unrealized losses existing for less than 12 months, unrealized losses	(4)
Continuous unrealized losses existing for greater than 12 months, fair value	0
Continuous unrealized losses existing for greater than 12 months, unrealized losses	0
Total, fair value	1,007
Total, unrealized losses	(4)
Collateralized mortgage obligations
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	1,046
Continuous unrealized losses existing for less than 12 months, unrealized losses	(9)
Continuous unrealized losses existing for greater than 12 months, fair value	0
Continuous unrealized losses existing for greater than 12 months, unrealized losses	0
Total, fair value	1,046
Total, unrealized losses	$ (9)