Investment Securities - Amortized cost and fair value for held to maturity and available for sale securities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Investment securities held-to-maturity
Amortized Cost	$ 1,955,754	$ 2,048,030
Gross Unrealized Losses	(314,712)	(315,180)
Fair Value	1,641,042	1,732,850
Investment securities available for sale
Amortized Cost	7,016,432	6,696,576
Gross Unrealized Gains	14,040	39,169
Gross Unrealized Losses	(432,295)	(421,989)
Fair Value	6,598,177	6,313,756
U.S. Government agencies
Investment securities held-to-maturity
Amortized Cost	132,915	132,913
Gross Unrealized Losses	(16,795)	(15,767)
Fair Value	116,120	117,146
Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Investment securities held-to-maturity
Amortized Cost	1,090,113	1,153,024
Gross Unrealized Losses	(175,475)	(177,101)
Fair Value	914,638	975,923
Investment securities available for sale
Amortized Cost	2,026,760	1,826,307
Gross Unrealized Gains	4,562	10,108
Gross Unrealized Losses	(144,756)	(138,307)
Fair Value	1,886,566	1,698,108
Residential collateralized mortgage-obligations issued by U.S. government agencies or sponsored enterprises
Investment securities held-to-maturity
Amortized Cost	363,925	379,107
Gross Unrealized Losses	(57,204)	(55,232)
Fair Value	306,721	323,875
Investment securities available for sale
Amortized Cost	2,082,757	2,208,710
Gross Unrealized Gains	5,511	23,979
Gross Unrealized Losses	(54,109)	(47,105)
Fair Value	2,034,159	2,185,584
Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Investment securities held-to-maturity
Amortized Cost	324,980	336,910
Gross Unrealized Losses	(57,187)	(58,332)
Fair Value	267,793	278,578
Investment securities available for sale
Amortized Cost	1,095,770	903,209
Gross Unrealized Gains	1,050	3,282
Gross Unrealized Losses	(79,341)	(74,042)
Fair Value	1,017,479	832,449
State and municipal obligations
Investment securities available for sale
Amortized Cost	1,240,617	1,141,377
Gross Unrealized Gains	2,484	1,252
Gross Unrealized Losses	(128,351)	(135,217)
Fair Value	1,114,750	1,007,412
Small Business Administration loan-backed securities
Investment securities held-to-maturity
Amortized Cost	43,821	46,076
Gross Unrealized Losses	(8,051)	(8,748)
Fair Value	35,770	37,328
Investment securities available for sale
Amortized Cost	547,528	593,973
Gross Unrealized Gains	433	548
Gross Unrealized Losses	(24,844)	(26,088)
Fair Value	523,117	568,433
Corporate securities
Investment securities available for sale
Amortized Cost	23,000	23,000
Gross Unrealized Losses	(894)	(1,230)
Fair Value	$ 22,106	$ 21,770

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

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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