Investment Securities (Schedule of Investment Securities) (Detail) - USD ($)	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Available-for-sale securities
Amortized Cost	$ 3,478,306,000	$ 2,316,369,000	$ 2,347,419,000
Gross Unrealized Gains	127,000	40,094,000	52,948,000
Gross Unrealized Losses	(554,780,000)	(28,670,000)	(26,889,000)
Fair Value	2,923,653,000	2,327,793,000	2,373,478,000
Held-to-maturity securities
Amortized Cost	3,390,152,000	2,942,363,000	2,736,805,000
Gross Unrealized Gains	203,000	10,609,000	12,727,000
Gross Unrealized Losses	(711,029,000)	(52,278,000)	(50,052,000)
Fair Value	2,679,326,000	2,900,694,000	2,699,480,000
Less: Allowance for credit losses	(310,000)	(78,000)	(83,000)
Held-to-maturity securities, net of allowance for credit losses	3,389,842,000	2,942,285,000	2,736,722,000
Equity securities with readily determinable fair value
Amortized Cost	120,073,000	86,989,000	83,909,000
Gross Unrealized Gains	2,233,000	5,354,000	5,678,000
Gross Unrealized Losses	(8,294,000)	(1,832,000)	(1,394,000)
Fair Value	114,012,000	90,511,000	88,193,000
U.S. Treasury
Available-for-sale securities
Amortized Cost	0	0	6,000,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	6,000,000
U.S. government agencies
Available-for-sale securities
Amortized Cost	50,000,000	50,158,000	50,163,000
Gross Unrealized Gains	0	2,349,000	3,112,000
Gross Unrealized Losses	(5,987,000)	0	0
Fair Value	44,013,000	52,507,000	53,275,000
Held-to-maturity securities
Amortized Cost	314,618,000	180,192,000	176,143,000
Gross Unrealized Gains	0	201,000	482,000
Gross Unrealized Losses	(72,723,000)	(3,314,000)	(2,878,000)
Fair Value	241,895,000	177,079,000	173,747,000
Municipal
Available-for-sale securities
Amortized Cost	181,612,000	161,618,000	170,612,000
Gross Unrealized Gains	127,000	4,193,000	4,202,000
Gross Unrealized Losses	(7,738,000)	(217,000)	(214,000)
Fair Value	174,001,000	165,594,000	174,600,000
Held-to-maturity securities
Amortized Cost	180,304,000	187,486,000	190,662,000
Gross Unrealized Gains	203,000	9,544,000	10,321,000
Gross Unrealized Losses	(7,791,000)	(223,000)	(334,000)
Fair Value	172,716,000	196,807,000	200,649,000
Corporate notes
Held-to-maturity securities
Amortized Cost	48,403,000	43,955,000	51,691,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(5,705,000)	(1,119,000)	(738,000)
Fair Value	42,698,000	42,836,000	50,953,000
Financial issuers
Available-for-sale securities
Amortized Cost	93,994,000	96,878,000	98,848,000
Gross Unrealized Gains	0	418,000	500,000
Gross Unrealized Losses	(7,951,000)	(2,599,000)	(1,241,000)
Fair Value	86,043,000	94,697,000	98,107,000
Other
Available-for-sale securities
Amortized Cost	1,000,000	1,000,000	1,000,000
Gross Unrealized Gains	0	7,000	11,000
Gross Unrealized Losses	(10,000)	0	0
Fair Value	990,000	1,007,000	1,011,000
Mortgage-backed securities
Available-for-sale securities
Amortized Cost	3,052,778,000	1,901,005,000	1,913,139,000
Gross Unrealized Gains	0	32,830,000	44,931,000
Gross Unrealized Losses	(513,978,000)	(25,854,000)	(25,434,000)
Fair Value	2,538,800,000	1,907,981,000	1,932,636,000
Held-to-maturity securities
Amortized Cost	2,679,862,000	2,530,730,000	2,318,309,000
Gross Unrealized Gains	0	864,000	1,924,000
Gross Unrealized Losses	(600,335,000)	(47,622,000)	(46,102,000)
Fair Value	2,079,527,000	2,483,972,000	2,274,131,000
Collateralized mortgage obligations
Available-for-sale securities
Amortized Cost	98,922,000	105,710,000	107,657,000
Gross Unrealized Gains	0	297,000	192,000
Gross Unrealized Losses	(19,116,000)	0	0
Fair Value	79,806,000	106,007,000	107,849,000
Held-to-maturity securities
Amortized Cost	166,965,000	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(24,475,000)	0	0
Fair Value	142,490,000	0	0
Mortgage-backed securities, subprime
Available-for-sale securities
Fair Value	$ 0	$ 0	$ 0