Investment Securities - Schedule of Available-for-sale Investment Securities Portfolios (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	$ 1,078,576,000
Continuous unrealized losses existing for less than 12 months, unrealized losses	(41,403,000)
Continuous unrealized losses existing for greater than 12 months, fair value	2,521,891,000
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(662,535,000)
Total, fair value	3,600,467,000
Total, unrealized losses	(703,938,000)
Available-for-sale securities, at fair value	3,611,835,000	$ 3,243,017,000	$ 2,923,653,000
U.S. government agencies
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	29,974,000
Continuous unrealized losses existing for less than 12 months, unrealized losses	(26,000)
Continuous unrealized losses existing for greater than 12 months, fair value	42,456,000
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(7,544,000)
Total, fair value	72,430,000
Total, unrealized losses	(7,570,000)
Available-for-sale securities, at fair value	72,430,000	74,222,000	44,013,000
Municipal
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	71,452,000
Continuous unrealized losses existing for less than 12 months, unrealized losses	(2,331,000)
Continuous unrealized losses existing for greater than 12 months, fair value	90,634,000
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(6,403,000)
Total, fair value	162,086,000
Total, unrealized losses	(8,734,000)
Available-for-sale securities, at fair value	168,523,000	168,655,000	174,001,000
Financial issuers
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	75,627,000
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(8,368,000)
Total, fair value	75,627,000
Total, unrealized losses	(8,368,000)
Available-for-sale securities, at fair value	75,627,000	84,703,000	86,043,000
Other
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	979,000
Continuous unrealized losses existing for less than 12 months, unrealized losses	(21,000)
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	979,000
Total, unrealized losses	(21,000)
Available-for-sale securities, at fair value	979,000	1,002,000	990,000
Residential mortgage-backed securities
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	963,794,000
Continuous unrealized losses existing for less than 12 months, unrealized losses	(38,223,000)
Continuous unrealized losses existing for greater than 12 months, fair value	2,242,942,000
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(617,912,000)
Total, fair value	3,206,736,000
Total, unrealized losses	(656,135,000)
Available-for-sale securities, at fair value	3,206,736,000	2,819,937,000	2,538,800,000
Commercial (multi-family) mortgage-backed securities
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, fair value	12,377,000
Continuous unrealized losses existing for less than 12 months, unrealized losses	(802,000)
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	12,377,000
Total, unrealized losses	(802,000)
Available-for-sale securities, at fair value	12,377,000
Collateralized mortgage obligations
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	70,232,000
Continuous unrealized losses existing for greater than 12 months, unrealized losses	(22,308,000)
Total, fair value	70,232,000
Total, unrealized losses	(22,308,000)
Available-for-sale securities, at fair value	70,232,000	79,550,000	79,806,000
Mortgage-backed securities, subprime
Available-for-sale securities
Available-for-sale securities, at fair value	$ 0	$ 0	$ 0