Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Cash Flows from Operating Activities
Net income	$ 73,384	$ 46,852
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	(13,558)	25,000
Provision for losses on other real estate owned	0	336
Deferred tax provision	6,135	(149)
Depreciation and amortization	2,044	1,797
Amortization of right-of-use asset	2,221	2,115
Change in operating lease liabilities	2,319	(1,083)
Net gains on sale and transfer of other real estate owned	0	(4,538)
Net gains on sale of loans	(289)	(3)
Proceeds from sales of loans	6,345	239
Originations of loans held for sale	(6,056)	(236)
Amortization on alternative energy partnerships, venture capital and other investments	11,641	13,923
Net gain on sales and calls of securities	(853)	(6)
Amortization/accretion of security premiums/discounts, net	2,282	1,676
Loss on sales or disposal of fixed assets	22	0
Unrealized loss on equity securities	2,752	6,102
Stock based compensation and stock issued to officers as compensation	1,243	1,543
Net change in accrued interest receivable and other assets	11,863	4,126
Net change in other liabilities	(9,924)	(2,661)
Net cash provided by operating activities	91,571	95,033
Cash Flows from Investing Activities
Purchase of investment securities available-for-sale	(50,450)	(89,989)
Proceeds from sale of investment securities available-for-sale	21,102	74,935
Proceeds from sale of equity securities	0	3,113
Proceeds from repayments, maturities and calls of investment securities available-for-sale	148,685	126,878
Redemptions of Federal Home Loan Bank stock	0	840
Net increase in loans	(15,246)	(458,616)
Purchase of premises and equipment	(760)	(867)
Proceeds from sales of other real estate owned	0	881
Net increase in investment in affordable housing and alternative energy partnerships	(5,950)	(18,696)
Net cash used for investing activities	97,381	(361,521)
Cash Flows from Financing Activities
Net increase in deposits	244,327	397,669
Advances from Federal Home Loan Bank	50,000	1,065,000
Repayment of Federal Home Loan Bank borrowings	(125,000)	(1,240,000)
Cash dividends paid	(24,650)	(24,659)
Repayment of other borrowings	0	58
Purchases of treasury stock	0	(12,880)
Repayment of short-term borrowings	0	(12,785)
Proceeds from shares issued under Dividend Reinvestment Plan	868	846
Taxes paid related to net share settlement of RSUs	(1,279)	(523)
Net cash provided by financing activities	144,266	172,726
Decrease in cash, cash equivalents, and restricted cash	333,218	(93,762)
Cash, cash equivalents, and restricted cash, beginning of the period	1,421,078	593,778	$ 593,778
Cash, cash equivalents, and restricted cash, end of the period	1,754,296	500,016	$ 1,421,078
Supplemental disclosure of cash flow information
Interest	25,872	51,248
Income taxes paid	2,891	2,642
Non-cash investing and financing activities:
Net change in unrealized holding loss on securities available-for-sale, net of tax	(4,887)	11,853
Net change in unrealized holding loss on cash flow hedge derivatives	$ 1,263	$ (4,278)