Investment Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Available for sale debt securities
Amortized Cost	$ 3,427,708,000	$ 3,549,599,000
Unrealized Gains		50,000
Unrealized Losses	(373,428,000)	(398,516,000)
Total available-for-sale securities, Fair value,	3,054,280,000	3,151,133,000
Held to maturity securities
Amortized Cost	4,261,361,000	4,320,639,000
Unrealized Gains	111,000
Unrealized Losses	(436,994,000)	(505,817,000)
Total held to maturity, Fair value,	3,824,478,000	3,814,822,000
Available-for-sale investment securities
Accrued interest receivable related to available-for-sale investment securities	8,900,000	8,900,000
Accrued interest receivable related to held to maturity investment securities	7,700,000	7,500,000
Reclassification of available for sale securities to held to maturity	0	4,600,000,000
Other comprehensive income (loss), transfer of securities from available for sale to held to maturity		(372,400,000)
Gains (losses) recognized on reclassification, transfer of securities from available for sale to held to maturity		0
Collateralized Loan Obligations
Available for sale debt securities
Amortized Cost	249,889,000	249,877,000
Unrealized Gains		50,000
Unrealized Losses	(12,478,000)	(8,606,000)
Total available-for-sale securities, Fair value,	237,411,000	241,321,000
U.S. Treasury and government agency debt securities
Available for sale debt securities
Amortized Cost	130,936,000	163,309,000
Unrealized Losses	(10,708,000)	(12,327,000)
Total available-for-sale securities, Fair value,	120,228,000	150,982,000
Held to maturity securities
Amortized Cost	54,386,000	54,318,000
Unrealized Losses	(4,694,000)	(5,674,000)
Total held to maturity, Fair value,	49,692,000	48,644,000
Government-sponsored enterprises debt securities
Available for sale debt securities
Amortized Cost	45,000,000	45,000,000
Unrealized Losses	(675,000)	(699,000)
Total available-for-sale securities, Fair value,	44,325,000	44,301,000
Residential - Government agency
Available for sale debt securities
Amortized Cost	65,261,000	66,792,000
Unrealized Losses	(5,964,000)	(7,069,000)
Total available-for-sale securities, Fair value,	59,297,000	59,723,000
Held to maturity securities
Amortized Cost	45,860,000	46,302,000
Unrealized Losses	(5,716,000)	(6,294,000)
Total held to maturity, Fair value,	40,144,000	40,008,000
Residential - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	1,276,130,000	1,317,718,000
Unrealized Losses	(143,876,000)	(157,263,000)
Total available-for-sale securities, Fair value,	1,132,254,000	1,160,455,000
Held to maturity securities
Amortized Cost	104,868,000	106,534,000
Unrealized Losses	(11,607,000)	(12,978,000)
Total held to maturity, Fair value,	93,261,000	93,556,000
Commercial - Government agency
Available for sale debt securities
Amortized Cost	281,009,000	282,700,000
Unrealized Losses	(45,938,000)	(44,847,000)
Total available-for-sale securities, Fair value,	235,071,000	237,853,000
Held to maturity securities
Amortized Cost	30,606,000	30,544,000
Unrealized Losses	(5,544,000)	(5,229,000)
Total held to maturity, Fair value,	25,062,000	25,315,000
Commercial - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	126,057,000	130,612,000
Unrealized Losses	(9,290,000)	(11,039,000)
Total available-for-sale securities, Fair value,	116,767,000	119,573,000
Held to maturity securities
Amortized Cost	1,147,009,000	1,150,449,000
Unrealized Gains	111,000
Unrealized Losses	(117,007,000)	(138,451,000)
Total held to maturity, Fair value,	1,030,113,000	1,011,998,000
Commercial - Non -agency
Available for sale debt securities
Amortized Cost	21,964,000	21,964,000
Unrealized Losses	(831,000)	(493,000)
Total available-for-sale securities, Fair value,	21,133,000	21,471,000
Government agency
Available for sale debt securities
Amortized Cost	715,004,000	738,524,000
Unrealized Losses	(78,402,000)	(85,202,000)
Total available-for-sale securities, Fair value,	636,602,000	653,322,000
Held to maturity securities
Amortized Cost	1,060,910,000	1,080,492,000
Unrealized Losses	(104,573,000)	(122,378,000)
Total held to maturity, Fair value,	956,337,000	958,114,000
Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	516,458,000	533,103,000
Unrealized Losses	(65,266,000)	(70,971,000)
Total available-for-sale securities, Fair value,	451,192,000	462,132,000
Held to maturity securities
Amortized Cost	1,763,805,000	1,798,178,000
Unrealized Losses	(181,013,000)	(207,045,000)
Total held to maturity, Fair value,	1,582,792,000	1,591,133,000
Debt securities issued by states and political subdivisions
Held to maturity securities
Amortized Cost	53,917,000	53,822,000
Unrealized Losses	(6,840,000)	(7,768,000)
Total held to maturity, Fair value,	$ 47,077,000	$ 46,054,000