Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Net income	$ 207,237,000	$ 150,102,000
Adjustments to reconcile net income to net cash provided by operating activities:
Reversal for credit losses	(4,500,000)	(2,500,000)
Provision for losses on other real estate owned		889,000
Deferred tax liability	2,342,000	10,319,000
Depreciation and amortization	5,593,000	5,416,000
Net gains on sale and transfer of other real estate owned	(567,000)	(394,000)
Proceeds from sales of loans	8,000,000	7,500,000
Amortization on alternative energy partnerships, venture capital and other investments	5,384,000	2,778,000
Net loss on sales and calls of securities	14,000	438,000
Amortization/accretion of security premiums/discounts, net	2,371,000	990,000
Loss on sales or disposal of fixed assets	107,000
Unrealized loss on equity securities	4,580,000
Stock based compensation and stock issued to officers as compensation	5,976,000	4,449,000
Net change in accrued interest receivable and other assets	(7,863,000)	(51,776,000)
Gain on acquisition	(340,000)	(5,440,000)
Net change in other liabilities	10,998,000	828,000
Net cash provided by operating activities	239,332,000	123,599,000
Cash Flows from Investing Activities
Purchase of investment securities available-for-sale	(448,805,000)	(450,745,000)
Proceeds from sale of investment securities available-for-sale	99,644,000	99,541,000
Proceeds from repayments, maturities and calls of investment securities available-for-sale	346,328,000	389,829,000
Purchase of Federal Home Loan Bank stock	(5,430,000)
Redemptions of Federal Home Loan Bank stock	11,265,000	6,459,000
Net increase in loans	(771,290,000)	(686,225,000)
Purchase of premises and equipment	(4,496,000)	(976,000)
Proceeds from sales of other real estate owned	3,302,000	2,186,000
Net increase in investment in affordable housing and alternative energy partnerships	(36,666,000)	(20,867,000)
Acquisition, net of cash acquired		(14,309,000)
Net cash used for investing activities	(806,148,000)	(675,107,000)
Cash Flows from Financing Activities
Net increase in deposits	890,823,000	73,120,000
Net decrease in federal funds purchased and securities sold under agreements to repurchase	(100,000,000)	(250,000,000)
Advances from Federal Home Loan Bank	4,495,000,000	2,608,000,000
Repayment of Federal Home Loan Bank borrowings	(4,610,000,000)	(2,393,000,000)
Cash dividends paid	(58,498,000)	(50,491,000)
Repayment of other borrowings	(37,117,000)
Proceeds from issuance of other borrowings	29,554,000
Proceeds from shares issued under Dividend Reinvestment Plan	1,982,000	1,849,000
Proceeds from exercise of stock options	838,000	1,018,000
Taxes paid related to net share settlement of RSUs	(3,550,000)	(5,127,000)
Net cash provided by (used in) financing activities	609,032,000	(14,631,000)
Increase/(decrease) in cash and cash equivalents	42,216,000	(566,139,000)
Cash and cash equivalents, beginning of the period	539,801,000	1,185,084,000
Cash and cash equivalents, end of the period	582,017,000	618,945,000
Supplemental disclosure of cash flow information
Interest	79,877,000	58,416,000
Income taxes paid	48,072,000	62,296,000
Non-cash investing and financing activities:
Net change in unrealized holding (loss)/gain on securities available-for-sale, net of tax	(16,793,000)	3,592,000
Net change in unrealized holding gain/(loss) on cash flow hedge derivatives	4,595,000	(94,000)
Transfers to other real estate owned from loans held for investment	$ 1,646,000	$ 726,000