Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2024	Mar. 30, 2024	Mar. 31, 2023	Dec. 31, 2023
Cash Flows from Operating Activities
Net income	$ 71,435	$ 71,435	$ 96,007
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	1,900		8,100
Deferred tax benefit	(4,782)		(7,293)
Depreciation and amortization	1,889		2,054
Amortization of right-of-use asset	2,477		2,405
Change in operating lease liabilities	(472)		81
Net gains on sale of loans	(20)		0
Loss on sales or disposal of premises and equipment	0		6
Amortization on alternative energy partnerships, venture capital and other investments	14,432		15,594
Net gains on sales of securities available-for-sale	(1,107)		0
Amortization/accretion of securities available-for-sale premiums/discounts, net	(6,370)		(1,324)
Unrealized loss/(gain) on equity securities	9,026		(4,853)
Write off of securities available-for-sale	0		3,000
Stock-based compensation and stock issued to officers as compensation	905		1,511
Net change in accrued interest receivable and other assets	(1,424)		15,608
Net change in other liabilities	281		(9,730)
Net cash provided by operating activities	88,170		121,166
Cash Flows from Investing Activities
Purchase of securities available-for-sale	(469,647)		(156,597)
Proceeds from repayments, maturities and calls of securities available-for-sale	384,721		104,669
Proceeds from sale of securities available-for-sale	33,690		0
Purchase of Federal Home Loan Bank stock	(12,535)		(680)
Redemption of Federal Home Loan Bank stock	13,031		680
Proceeds from sale of loans originally classified as held-for-investment	83,803		0
Net increase/(decrease) in loans	10,634		(68,133)
Purchase of premises and equipment	(916)		(295)
Net increase in affordable housing investments and alternative energy partnerships	(5,680)		(8,078)
Net cash provided/(used) for investing activities	37,101		(128,434)
Cash Flows from Financing Activities
Increase in deposits	520,843		143,633
Advances from Federal Home Loan Bank	4,403,000		2,075,000
Repayment of Federal Home Loan Bank borrowings	(4,678,000)		(2,200,000)
Cash dividends paid	(24,708)		(24,605)
Purchases of treasury stock	8		(16,736)
Proceeds from shares issued under Dividend Reinvestment Plan	744		918
Taxes paid related to net share settlement of RSUs	(24)		(14)
Net cash provided/(used) by financing activities	221,863		(21,804)
Increase/(decrease) in cash, cash equivalents, and restricted cash	347,134		(29,072)
Cash, cash equivalents, and restricted cash, beginning of the period	828,801	$ 828,801	1,162,402	$ 1,162,402
Cash, cash equivalents, and restricted cash, end of the period	1,175,935		1,133,330	$ 828,801
Supplemental disclosure of cash flow information
Interest	155,048		86,785
Income taxes paid	282		0
Non-cash investing and financing activities:
Net change in unrealized holding (loss)/gain on securities available-for-sale, net of tax	(6,422)		11,659
Net change in unrealized holding loss on cash flow hedge derivatives	(441)		(441)
Loans transferred from held-for-investment to held-for-sale	$ 106,953		$ 0