Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Available-for-Sale:
Available-for-Sale: Amortized Cost	$ 3,172,436	$ 4,320,884
Available-for-Sale: Gross Unrealized Gains	1,851	21,460
Available-for-Sale: Gross Unrealized Losses	(329,464)	(66,288)
Available-for-Sale: Fair Value	2,844,823	4,276,056
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	5,414,139	4,694,780
Held-to-Maturity: Gross Unrealized Gains	43	28,334
Held-to-Maturity: Gross Unrealized Losses	(798,789)	(76,495)
Held-to-Maturity: Fair Value	4,615,393	4,646,619
Debt Securities Issued by the U.S. Treasury and Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	248,335	248,858
Available-for-Sale: Gross Unrealized Gains	638	1,513
Available-for-Sale: Gross Unrealized Losses	(15,067)	(284)
Available-for-Sale: Fair Value	233,906	250,087
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	131,619	131,495
Held-to-Maturity: Gross Unrealized Gains		287
Held-to-Maturity: Gross Unrealized Losses	(18,202)	(643)
Held-to-Maturity: Fair Value	113,417	131,139
Debt Securities Issued by States and Political Subdivisions
Available-for-Sale:
Available-for-Sale: Amortized Cost	107,689	74,743
Available-for-Sale: Gross Unrealized Gains	158	1,080
Available-for-Sale: Gross Unrealized Losses	(12,582)	(5)
Available-for-Sale: Fair Value	95,265	75,818
Debt Securities Issued by Government-Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	48,807	1,758
Available-for-Sale: Gross Unrealized Gains		33
Available-for-Sale: Gross Unrealized Losses	(179)	(11)
Available-for-Sale: Fair Value	48,628	1,780
Debt Securities Issued by Corporations
Available-for-Sale:
Available-for-Sale: Amortized Cost	850,585	384,590
Available-for-Sale: Gross Unrealized Gains	809	2,339
Available-for-Sale: Gross Unrealized Losses	(56,736)	(3,816)
Available-for-Sale: Fair Value	794,658	383,113
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	17,014	20,316
Held-to-Maturity: Gross Unrealized Gains		76
Held-to-Maturity: Gross Unrealized Losses	(2,534)	(249)
Held-to-Maturity: Fair Value	14,480	20,143
Residential - Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	828,798	1,327,990
Available-for-Sale: Gross Unrealized Gains	245	9,818
Available-for-Sale: Gross Unrealized Losses	(96,215)	(18,766)
Available-for-Sale: Fair Value	732,828	1,319,042
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	1,848,239	1,774,394
Held-to-Maturity: Gross Unrealized Gains	35	12,139
Held-to-Maturity: Gross Unrealized Losses	(294,047)	(30,621)
Held-to-Maturity: Fair Value	1,554,227	1,755,912
Residential - U.S. Government-Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	919,980	2,127,781
Available-for-Sale: Gross Unrealized Gains	1	4,792
Available-for-Sale: Gross Unrealized Losses	(126,110)	(42,247)
Available-for-Sale: Fair Value	793,871	2,090,326
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	2,968,322	2,286,880
Held-to-Maturity: Gross Unrealized Gains	8	15,508
Held-to-Maturity: Gross Unrealized Losses	(397,055)	(32,627)
Held-to-Maturity: Fair Value	2,571,275	2,269,761
Commercial - Government Agencies - Sponsored Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	168,242	155,164
Available-for-Sale: Gross Unrealized Gains		1,885
Available-for-Sale: Gross Unrealized Losses	(22,575)	(1,159)
Available-for-Sale: Fair Value	145,667	155,890
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	448,945	481,695
Held-to-Maturity: Gross Unrealized Gains		324
Held-to-Maturity: Gross Unrealized Losses	(86,951)	(12,355)
Held-to-Maturity: Fair Value	361,994	469,664
Mortgage-Backed Securities
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,917,020	3,610,935
Available-for-Sale: Gross Unrealized Gains	246	16,495
Available-for-Sale: Gross Unrealized Losses	(244,900)	(62,172)
Available-for-Sale: Fair Value	1,672,366	3,565,258
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	5,265,506	4,542,969
Held-to-Maturity: Gross Unrealized Gains	43	27,971
Held-to-Maturity: Gross Unrealized Losses	(778,053)	(75,603)
Held-to-Maturity: Fair Value	$ 4,487,496	$ 4,495,337

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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