Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities
Net income	$ 228,860	$ 279,135	$ 271,885
Adjustments to reconcile net income to net cash provided by operating activities:
Provision/(reversal) for credit losses	57,500	(7,000)	(4,500)
Provision for losses on other real estate owned	717	681	0
Deferred tax provision	(9,486)	9,825	2,343
Depreciation and amortization	7,660	6,756	7,314
Amortization of right-of-use asset	8,852	8,366	0
Change in operating lease liabilities	(2,389)	(7,157)	0
Net gains on sale and transfers of other real estate owned	(4,216)	(212)	(1,187)
Net gains on sale of loans	(413)	(804)	0
Proceeds from sale of loans	11,098	75,257	8,000
Originations of loans held for sale	(10,685)	(2,241)	0
Loss on sales or disposal of fixed assets	45	14	107
Amortization of alternative energy partnerships, venture capital and other investments	58,131	39,898	40,871
Gain on sales and calls of securities	(1,695)	(211)	(22)
Other non-cash interest income	0	0	(1,576)
Amortization of security premiums, net	8,617	3,834	3,018
Loss/(gain) on equity securities	1,148	(5,736)	2,787
Stock based and stock issued to officers and directors compensation expense	6,406	7,350	7,974
Net change in accrued interest receivable and other assets	(21,247)	6,163	(13,984)
Gain from acquisition	0	0	(340)
Net change in other liabilities	(18,948)	21,061	13,848
Net cash provided by operating activities	319,955	434,979	336,538
Cash Flows from Investing Activities
Decrease in interest bearing deposits	0	0	5,000
Purchase of investment securities available-for-sale	(434,165)	(770,206)	(497,787)
Proceeds from repayment, maturity, and call of investment securities available-for-sale	734,485	296,721	447,773
Proceeds from sale of investment securities available-for-sale	117,249	293,849	99,899
Proceeds from sale of equity securities	3,112	2,829	0
Purchase of Federal Home Loan Bank stock	(840)	(1,815)	(5,430)
Redemption of Federal Home Loan Bank stock	1,680	975	11,265
Net increase in loans	(583,136)	(1,147,019)	(1,125,623)
Purchase of premises and equipment	(5,778)	(7,133)	(6,670)
Proceeds from sales of other real estate owned	4,308	2,822	3,820
Increase in investment in affordable housing and alternative energy partnerships	(79,119)	(52,697)	(66,574)
Net cash used in investing activities	(242,204)	(1,381,674)	(1,134,327)
Cash Flows from Financing Activities
Net increase in deposits	1,417,310	989,942	1,012,284
Net decrease in federal funds purchased and securities sold under agreements to repurchase	0	0	(100,000)
Advances from Federal Home Loan Bank	1,450,000	4,355,000	5,130,000
Repayment of Federal Home Loan Bank borrowings	(1,970,000)	(4,215,000)	(5,030,000)
Cash dividends	(98,688)	(99,131)	(83,428)
Purchase of treasury stock	(23,593)	(36,301)	(42,648)
Proceeds from issuance of short-term borrowings	0	25,683	0
Repayment of short-term borrowings	(25,683)	0	0
Repayment of long-term debt and other borrowings	(7,663)	(81,065)	(23,040)
Proceeds from shares issued to Dividend Reinvestment Plan	9,777	3,366	2,822
Proceeds from exercise of stock options	0	0	838
Taxes paid related to net share settlement of RSUs	(1,911)	(2,311)	(3,550)
Net cash provided by financing activities	749,549	940,183	863,278
Increase/(Decrease) in cash, cash equivalents, and restricted cash	827,300	(6,512)	65,489
Cash, cash equivalents, and restricted cash, beginning of the year	593,778	600,290	534,801
Cash, cash equivalents, and restricted cash, end of the year	1,421,078	593,778	600,290
Supplemental disclosure of cash flow information
Interest	162,434	182,527	116,524
Income taxes	45,371	61,548	65,866
Non-cash investing and financing activities:
Net change in unrealized holding gain/(loss) on securities available-for-sale, net of tax	6,486	23,479	(7,949)
Net change in unrealized (loss)/gain on interest rate swaps designated as cash flow hedges	(3,478)	(3,171)	1,525
Transfers to other real estate owned from loans held for investment	0	860	5,476
Loans transferred to loans held for sale	$ 0	$ 75,285	$ 0