Investment Securities - Schedule of Investment Securities (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Available-for-sale securities
Amortized Cost	$ 4,315,723,000	$ 3,769,634,000	$ 3,478,306,000
Gross Unrealized Gains	50,000	511,000	127,000
Gross Unrealized Losses	(703,938,000)	(527,128,000)	(554,780,000)
Fair Value	3,611,835,000	3,243,017,000	2,923,653,000
Held-to-maturity securities
Amortized Cost	3,909,531,000	3,641,055,000	3,390,152,000
Gross Unrealized Gains	123,000	477,000	203,000
Gross Unrealized Losses	(851,695,000)	(691,711,000)	(711,029,000)
Fair Value	3,057,959,000	2,949,821,000	2,679,326,000
Less: Allowance for credit losses	(381,000)	(488,000)	(310,000)
Held-to-maturity securities, net of allowance for credit losses	3,909,150,000	3,640,567,000	3,389,842,000
Equity securities with readily determinable fair value
Amortized Cost	140,749,000	115,552,000	120,073,000
Gross Unrealized Gains	3,290,000	2,935,000	2,233,000
Gross Unrealized Losses	(9,729,000)	(8,122,000)	(8,294,000)
Fair Value	134,310,000	110,365,000	114,012,000
U.S. Treasury
Available-for-sale securities
Amortized Cost	4,930,000	14,943,000	0
Gross Unrealized Gains	1,000	5,000	0
Gross Unrealized Losses	0	0	0
Fair Value	4,931,000	14,948,000	0
U.S. government agencies
Available-for-sale securities
Amortized Cost	80,000,000	80,000,000	50,000,000
Gross Unrealized Gains	0	36,000	0
Gross Unrealized Losses	(7,570,000)	(5,814,000)	(5,987,000)
Fair Value	72,430,000	74,222,000	44,013,000
Held-to-maturity securities
Amortized Cost	339,598,000	339,614,000	314,618,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(87,897,000)	(75,293,000)	(72,723,000)
Fair Value	251,701,000	264,321,000	241,895,000
Municipal
Available-for-sale securities
Amortized Cost	177,208,000	173,861,000	181,612,000
Gross Unrealized Gains	49,000	230,000	127,000
Gross Unrealized Losses	(8,734,000)	(5,436,000)	(7,738,000)
Fair Value	168,523,000	168,655,000	174,001,000
Held-to-maturity securities
Amortized Cost	176,262,000	179,027,000	180,304,000
Gross Unrealized Gains	123,000	477,000	203,000
Gross Unrealized Losses	(11,230,000)	(4,066,000)	(7,791,000)
Fair Value	165,155,000	175,438,000	172,716,000
Corporate notes
Held-to-maturity securities
Amortized Cost	57,717,000	58,232,000	48,403,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(4,849,000)	(5,348,000)	(5,705,000)
Fair Value	52,868,000	52,884,000	42,698,000
Financial issuers
Available-for-sale securities
Amortized Cost	83,995,000	93,994,000	93,994,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(8,368,000)	(9,291,000)	(7,951,000)
Fair Value	75,627,000	84,703,000	86,043,000
Other
Available-for-sale securities
Amortized Cost	1,000,000	1,000,000	1,000,000
Gross Unrealized Gains	0	2,000	0
Gross Unrealized Losses	(21,000)	0	(10,000)
Fair Value	979,000	1,002,000	990,000
Residential mortgage-backed securities
Available-for-sale securities
Amortized Cost	3,862,871,000	3,308,494,000	3,052,778,000
Gross Unrealized Gains	0	238,000	0
Gross Unrealized Losses	(656,135,000)	(488,795,000)	(513,978,000)
Fair Value	3,206,736,000	2,819,937,000	2,538,800,000
Held-to-maturity securities
Amortized Cost	3,082,314,000	2,900,031,000	2,679,862,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(717,444,000)	(583,682,000)	(600,335,000)
Fair Value	2,364,870,000	2,316,349,000	2,079,527,000
Commercial (multi-family) mortgage-backed securities
Available-for-sale securities
Amortized Cost	13,179,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(802,000)
Fair Value	12,377,000
Held-to-maturity securities
Amortized Cost	6,425,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(477,000)
Fair Value	5,948,000
Collateralized mortgage obligations
Available-for-sale securities
Amortized Cost	92,540,000	97,342,000	98,922,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(22,308,000)	(17,792,000)	(19,116,000)
Fair Value	70,232,000	79,550,000	79,806,000
Held-to-maturity securities
Amortized Cost	247,215,000	164,151,000	166,965,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	(29,798,000)	(23,322,000)	(24,475,000)
Fair Value	217,417,000	140,829,000	142,490,000
Mortgage-backed securities, subprime
Available-for-sale securities
Fair Value	$ 0	$ 0	$ 0