Regulatory Capital - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 01, 2020	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2022
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Allowance for credit losses		$ 1,413,621	$ 1,416,048	$ 1,413,621	$ 1,416,048	$ 1,339,772	$ 1,269,652	$ 1,364,716	$ 1,357,075
Liability for unfunded commitments		91,959	113,847	91,959	113,847	112,962	$ 49,479	$ 62,600	124,924
Retained earnings		4,034,640		4,034,640		3,624,859
Unrealized gain (loss)				(69,000)		(115,000)
Unrealized loss, tax benefit				22,000		37,000
Dividends		116,000	$ 100,000	414,000	$ 400,000
Adjustments
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Period of deferment	2 years
Percentage amount deferred per year	25.00%
Percentage amount phased in during year	25.00%
Allowance for credit losses	$ 1,100,000	(259,536)		(259,536)		(259,536)			(259,536)
Liability for unfunded commitments	116,000	(26,095)		(26,095)		(26,094)			(26,094)
Deferred tax asset	306,000	(76,543)		(76,543)		(76,542)			(76,542)
Retained earnings	$ 953,000	$ (209,088)		$ (209,088)		$ (209,088)			$ (209,088)