Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Available-for-Sale:
Available-for-Sale: Amortized Cost	$ 4,320,884	$ 3,721,636	$ 2,607,636
Available-for-Sale: Gross Unrealized Gains	21,460	72,428	21,143
Available-for-Sale: Gross Unrealized Losses	(66,288)	(2,375)	(9,776)
Available-for-Sale: Fair Value	4,276,056	3,791,689	2,619,003
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	4,694,780	3,262,727	3,042,294
Held-to-Maturity: Gross Unrealized Gains	28,334	86,494	29,990
Held-to-Maturity: Gross Unrealized Losses	(76,495)	(528)	(9,402)
Held-to-Maturity: Fair Value	4,646,619	3,348,693	3,062,882
Debt Securities Issued by the U.S. Treasury and Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	248,858	174,409	222,365
Available-for-Sale: Gross Unrealized Gains	1,513	427	213
Available-for-Sale: Gross Unrealized Losses	(284)	(591)	(1,447)
Available-for-Sale: Fair Value	250,087	174,245	221,131
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	131,495	7,500	274,375
Held-to-Maturity: Gross Unrealized Gains	287	8	1,319
Held-to-Maturity: Gross Unrealized Losses	(643)	(8)	(31)
Held-to-Maturity: Fair Value	131,139	7,500	275,663
Debt Securities Issued by States and Political Subdivisions
Available-for-Sale:
Available-for-Sale: Amortized Cost	74,743	23,540	54,480
Available-for-Sale: Gross Unrealized Gains	1,080	1,301	631
Available-for-Sale: Gross Unrealized Losses	(5)	(1)	(14)
Available-for-Sale: Fair Value	75,818	24,840	55,097
Held-to-Maturity:
Held-to-Maturity: Amortized Cost		33,763	54,811
Held-to-Maturity: Gross Unrealized Gains		741	1,236
Held-to-Maturity: Fair Value		34,504	56,047
Debt Securities Issued by Government-Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,758	985	22,128
Available-for-Sale: Gross Unrealized Gains	33	77	19
Available-for-Sale: Gross Unrealized Losses	(11)	0	0
Available-for-Sale: Fair Value	1,780	1,062	22,147
Debt Securities Issued by Corporations
Available-for-Sale:
Available-for-Sale: Amortized Cost	384,590	220,717	335,553
Available-for-Sale: Gross Unrealized Gains	2,339	4,844	1,401
Available-for-Sale: Gross Unrealized Losses	(3,816)	(956)	(633)
Available-for-Sale: Fair Value	383,113	224,605	336,321
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	20,316	12,031	14,975
Held-to-Maturity: Gross Unrealized Gains	76	251
Held-to-Maturity: Gross Unrealized Losses	(249)		(138)
Held-to-Maturity: Fair Value	20,143	12,282	14,837
Residential - Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,327,990	1,561,603	1,164,466
Available-for-Sale: Gross Unrealized Gains	9,818	33,657	11,627
Available-for-Sale: Gross Unrealized Losses	(18,766)	(445)	(3,267)
Available-for-Sale: Fair Value	1,319,042	1,594,815	1,172,826
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	1,774,394	917,459	1,067,416
Held-to-Maturity: Gross Unrealized Gains	12,139	30,580	13,247
Held-to-Maturity: Gross Unrealized Losses	(30,621)	(29)	(5,348)
Held-to-Maturity: Fair Value	1,755,912	948,010	1,075,315
Residential - U.S. Government-Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	2,127,781	1,497,353	584,272
Available-for-Sale: Gross Unrealized Gains	4,792	21,254	4,363
Available-for-Sale: Gross Unrealized Losses	(42,247)	(324)	(1,874)
Available-for-Sale: Fair Value	2,090,326	1,518,283	586,761
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	2,286,880	2,099,053	1,546,479
Held-to-Maturity: Gross Unrealized Gains	15,508	51,735	13,871
Held-to-Maturity: Gross Unrealized Losses	(32,627)	(291)	(2,478)
Held-to-Maturity: Fair Value	2,269,761	2,150,497	1,557,872
Commercial - Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	155,164	243,029	224,372
Available-for-Sale: Gross Unrealized Gains	1,885	10,868	2,889
Available-for-Sale: Gross Unrealized Losses	(1,159)	(58)	(2,541)
Available-for-Sale: Fair Value	155,890	253,839	224,720
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	481,695	192,921	84,238
Held-to-Maturity: Gross Unrealized Gains	324	3,179	317
Held-to-Maturity: Gross Unrealized Losses	(12,355)	(200)	(1,407)
Held-to-Maturity: Fair Value	469,664	195,900	83,148
Mortgage-Backed Securities
Available-for-Sale:
Available-for-Sale: Amortized Cost	3,610,935	3,301,985	1,973,110
Available-for-Sale: Gross Unrealized Gains	16,495	65,779	18,879
Available-for-Sale: Gross Unrealized Losses	(62,172)	(827)	(7,682)
Available-for-Sale: Fair Value	3,565,258	3,366,937	1,984,307
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	4,542,969	3,209,433	2,698,133
Held-to-Maturity: Gross Unrealized Gains	27,971	85,494	27,435
Held-to-Maturity: Gross Unrealized Losses	(75,603)	(520)	(9,233)
Held-to-Maturity: Fair Value	$ 4,495,337	$ 3,294,407	$ 2,716,335

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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Amortized cost of 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 of 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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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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