Investment Securities (Schedule of Investment Securities Portfolio Continuous Unrealized Loss Position) (Detail) $ in Thousands	Jun. 30, 2022 USD ($)
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	$ 2,388,657
Continuous unrealized losses existing for less than 12 months, unrealized losses	(256,844)
Continuous unrealized losses existing for greater than 12 months, fair value	514,784
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(105,135)
Total, fair value	2,903,441
Total, unrealized losses	(361,979)
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	48,087
Continuous unrealized losses existing for less than 12 months, unrealized losses	(1,913)
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	48,087
Total, unrealized losses	(1,913)
Municipal
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	100,593
Continuous unrealized losses existing for less than 12 months, unrealized losses	(3,587)
Continuous unrealized losses existing for greater than 12 months, fair value	11,811
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(546)
Total, fair value	112,404
Total, unrealized losses	(4,133)
Financial issuers
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	21,256
Continuous unrealized losses existing for less than 12 months, unrealized losses	(744)
Continuous unrealized losses existing for greater than 12 months, fair value	67,561
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(4,433)
Total, fair value	88,817
Total, unrealized losses	(5,177)
Other
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	996
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	996
Total, unrealized losses	(4)
Mortgage-backed securities
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	2,130,876
Continuous unrealized losses existing for less than 12 months, unrealized losses	(236,361)
Continuous unrealized losses existing for greater than 12 months, fair value	435,412
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(100,156)
Total, fair value	2,566,288
Total, unrealized losses	(336,517)
Collateralized mortgage obligations
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	86,849
Continuous unrealized losses existing for less than 12 months, unrealized losses	(14,235)
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	86,849
Total, unrealized losses	$ (14,235)